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Earth and Planetary Sciences › Atmospheric Science

Tropical and Extratropical Cyclones Research

Works Count: 51859

Description

This cluster of papers focuses on the relationship between tropical cyclone intensity and climate change, including the impact of global warming, sea level rise, and environmental factors such as ENSO and wind shear. It also examines trends in tropical cyclone activity and the associated storm surge risks.

Keywords

Tropical Cyclones; Climate Change; Hurricanes; Storm Surge; Global Warming; Intensity; Trends; Sea Level Rise; ENSO; Wind Shear

Probabilistic 21st and 22nd century sea‐level projections at a global network of tide‐gauge sites

2014-06-13
Robert E. Kopp , Radley Horton , Christopher M. Little +5 more
Abstract Sea‐level rise due to both climate change and non‐climatic factors threatens coastal settlements, infrastructure, and ecosystems. Projections of mean global sea‐level (GSL) rise provide insufficient information to plan adaptive … Abstract Sea‐level rise due to both climate change and non‐climatic factors threatens coastal settlements, infrastructure, and ecosystems. Projections of mean global sea‐level (GSL) rise provide insufficient information to plan adaptive responses; local decisions require local projections that accommodate different risk tolerances and time frames and that can be linked to storm surge projections. Here we present a global set of local sea‐level (LSL) projections to inform decisions on timescales ranging from the coming decades through the 22nd century. We provide complete probability distributions, informed by a combination of expert community assessment, expert elicitation, and process modeling. Between the years 2000 and 2100, we project a very likely (90% probability) GSL rise of 0.5–1.2 m under representative concentration pathway (RCP) 8.5, 0.4–0.9 m under RCP 4.5, and 0.3–0.8 m under RCP 2.6. Site‐to‐site differences in LSL projections are due to varying non‐climatic background uplift or subsidence, oceanographic effects, and spatially variable responses of the geoid and the lithosphere to shrinking land ice. The Antarctic ice sheet (AIS) constitutes a growing share of variance in GSL and LSL projections. In the global average and at many locations, it is the dominant source of variance in late 21st century projections, though at some sites oceanographic processes contribute the largest share throughout the century. LSL rise dramatically reshapes flood risk, greatly increasing the expected number of “1‐in‐10” and “1‐in‐100” year events.
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The International Best Track Archive for Climate Stewardship (IBTrACS)

2009-09-28
Kenneth R. Knapp , Michael C. Kruk , David H. Levinson +2 more
The goal of the International Best Track Archive for Climate Stewardship (IBTrACS) project is to collect the historical tropical cyclone best-track data from all available Regional Specialized Meteorological Centers (RSMCs) … The goal of the International Best Track Archive for Climate Stewardship (IBTrACS) project is to collect the historical tropical cyclone best-track data from all available Regional Specialized Meteorological Centers (RSMCs) and other agencies, combine the disparate datasets into one product, and disseminate in formats used by the tropical cyclone community. Each RSMC forecasts and monitors storms for a specific region and annually archives best-track data, which consist of information on a storm's position, intensity, and other related parameters. IBTrACS is a new dataset based on the best-track data from numerous sources. Moreover, rather than preferentially selecting one track and intensity for each storm, the mean position, the original intensities from the agencies, and summary statistics are provided. This article discusses the dataset construction, explores the tropical cyclone climatology from IBTrACS, and concludes with an analysis of uncertainty in the tropical cyclone intensity record.
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On Formation and Intensification of Tropical Cyclones Through Latent Heat Release by Cumulus Convection

1965-01-01
H. L. Kuo
The effect on large scale motions of latent heat release by deep cumulus convection in a conditionally unstable atmosphere is investigated and a method devised to include this effect directly … The effect on large scale motions of latent heat release by deep cumulus convection in a conditionally unstable atmosphere is investigated and a method devised to include this effect directly in the equations for large scale flow. This method is then applied to the hurricane formation problem by incorporating it into time-dependent, circular symmetric dynamic hurricane models, either in gradient-wind balance or unbalanced. Numerical integrations of a two-level approximation of the balanced model have been carried out for two different formulations of the problem (including or not including a frictional radial flow), both starting from a hypothetical initial state characterized by a weak barotropic circular vortex with a maximum tangential velocity of 10 m sec−1 at a distance of 141.2 km from the center. The results obtained without frictional radial flow showed slow intensification of the tangential flow, to about 25 m sec−1, and establishment of a strong radial temperature gradient in the upper troposphere, from sixteen to twenty-four hours after the initial time, after which a steady state ensued. The radial flow obtained from this model remained less than 2 m sec−1. On the other hand, the results obtained with a superimposed frictional radial flow either decayed after reaching a moderate tangential velocity, or developed very rapidly after attaining higher velocity, and did not approach any steady state. The results further show that while the two-level approximation of the balanced model is able to reveal many important aspects of the development problem, it is not able to describe the further development associated with the upper level temperature gradient.
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Modeled Impact of Anthropogenic Warming on the Frequency of Intense Atlantic Hurricanes

2010-01-21
Morris A. Bender , Thomas R. Knutson , Robert E. Tuleya +4 more
Stormy Weather One of the most active questions about the effects of global warming is whether, and how, it might affect the frequency and the strength of hurricanes. Some studies … Stormy Weather One of the most active questions about the effects of global warming is whether, and how, it might affect the frequency and the strength of hurricanes. Some studies have suggested that warming will bring fewer, and less energetic, hurricanes, while others have claimed that we can expect more intense storms. Bender et al. (p. 454 ; see the news story by Kerr ) explore the influence of global warming on hurricane dynamics over the Atlantic Ocean with a state-of-the-art hurricane prediction model. The model predicts that the annual total number of hurricanes in the 21st century will be less than now, but also that the number of the most intense storms per year will increase. The largest increase of the most intense hurricane frequency is predicted in the western Atlantic, which suggests that Hispaniola, the Bahamas, and the Southeast coast of the United States could be at greater risk.
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Mesoscale convective systems

2004-12-01
Robert A. Houze
Mesoscale convective systems (MCSs) have regions of both convective and stratiform precipitation, and they develop mesoscale circulations as they mature. The upward motion takes the form of a deep‐layer ascent … Mesoscale convective systems (MCSs) have regions of both convective and stratiform precipitation, and they develop mesoscale circulations as they mature. The upward motion takes the form of a deep‐layer ascent drawn into the MCS in response to the latent heating and cooling in the convective region. The ascending layer overturns as it rises but overall retains a coherent layer structure. A middle level layer of inflow enters the stratiform region of the MCS from a direction determined by the large‐scale flow and descends in response to diabatic cooling at middle‐to‐low levels. A middle level mesoscale convective vortex (MCV) develops in the stratiform region, prolongs the MCS, and may contribute to tropical cyclone development. The propagation of an MCS may have a discrete component but may further be influenced by waves and disturbances generated both in response to the MCS and external to the MCS. Waves of a larger scale may affect the propagation velocity by phase locking with the MCS in a cooperative mode. The horizontal scale of an MCS may be limited either by a balance between the formation rate of convective precipitation and dissipation of stratiform precipitation or by the Rossby radius of the MCV. The vertical redistribution of momentum by an MCS depends on the size of the stratiform region, while the net vertical profile of heating of the large‐scale environment depends on the amount of stratiform rain. Regional variability of the stratiform rain from MCSs affects the large‐scale circulation's response to MCS heating.
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The increasing intensity of the strongest tropical cyclones

2008-09-01
James B. Elsner , James P. Kossin , Thomas H. Jagger

The Naval Research Laboratory’s Coupled Ocean/Atmosphere Mesoscale Prediction System (COAMPS)

1997-07-01
Richard M. Hodur
The three-dimensional Coupled Ocean/Atmosphere Mesoscale Prediction System (COAMPS) has been developed by the Naval Research Laboratory. COAMPS consists of an atmospheric data assimilation system comprising data quality control, analysis, initialization, … The three-dimensional Coupled Ocean/Atmosphere Mesoscale Prediction System (COAMPS) has been developed by the Naval Research Laboratory. COAMPS consists of an atmospheric data assimilation system comprising data quality control, analysis, initialization, and nonhydrostatic forecast model components, as well as a hydrostatic ocean model. The models can be integrated simultaneously so that the surface fluxes of heat, momentum, and moisture are exchanged across the air–water interface every time step. Optionally, either the atmospheric or ocean model can be used as a stand-alone system. The atmospheric component of COAMPS was used for operational support for the America3 team in the 1995 America’s Cup races. Results of these forecasts indicated the necessity of data assimilation to reduce model spinup in the first 6 h of the forecast. Accurate forecasts of the low-level wind in the coastal race area was accomplished by utilizing triply nested grids to attain the necessary high resolution to resolve the local wind patterns and the underlying surface terrain field. Two idealized simulations of a tropical cyclone were performed with COAMPS. In the first simulation, only the atmospheric model was used, assuming a fixed sea surface temperature (SST). A realistic structure developed with spiral bands of convection present outside the inner eyewall. These spiral bands occasionally contracted inward resulting in rapid fluctuations in the intensity of the tropical cyclone. In the second simulation, the ocean model was run simultaneously with the atmospheric model. The SST cooled over 8°C over a small area within the radius of maximum winds, resulting in a much weaker system. However, there appeared to be little effect on the overall strength of the system, as measured by the tangential velocities outside the radius of maximum winds.

Synoptic-Dynamic Climatology of the “Bomb”

1980-10-01
Frederick Sanders , John R. Gyakum
By defining a “bomb” as an extratropical surface cyclone whose central pressure fall averages at least 1 mb h−1 for 24 h, we have studied this explosive cyclogenesis in the … By defining a “bomb” as an extratropical surface cyclone whose central pressure fall averages at least 1 mb h−1 for 24 h, we have studied this explosive cyclogenesis in the Northern Hemisphere during the period September 1976–May 1979. This predominantly maritime, cold-season event is usually found ∼400 n mi downstream from a mobile 500 mb trough, within or poleward of the maximum westerlies, and within or ahead of the planetary-scale troughs. A more detailed examination of bombs (using a 12 h development criterion) was performed during the 1978–79 season. A survey of sea surface temperatures (SST's) in and around the cyclone center indicates explosive development occurs over a wide range of SST's, but, preferentially, near the strongest gradients. A quasi-geostrophic diagnosis of a composite incipient bomb indicates instantaneous pressure falls far short of observed rates. A test of current National Meteorological Center models shows these products also fall far short in attempting to capture observed rapid deepening.
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Atlantic Hurricane Database Uncertainty and Presentation of a New Database Format

2013-01-18
Christopher W. Landsea , James L. Franklin
Abstract “Best tracks” are National Hurricane Center (NHC) poststorm analyses of the intensity, central pressure, position, and size of Atlantic and eastern North Pacific basin tropical and subtropical cyclones. This … Abstract “Best tracks” are National Hurricane Center (NHC) poststorm analyses of the intensity, central pressure, position, and size of Atlantic and eastern North Pacific basin tropical and subtropical cyclones. This paper estimates the uncertainty (average error) for Atlantic basin best track parameters through a survey of the NHC Hurricane Specialists who maintain and update the Atlantic hurricane database. A comparison is then made with a survey conducted over a decade ago to qualitatively assess changes in the uncertainties. Finally, the implications of the uncertainty estimates for NHC analysis and forecast products as well as for the prediction goals of the Hurricane Forecast Improvement Program are discussed.
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Sensitivity of Tropical Cyclones to Surface Exchange Coefficients and a Revised Steady-State Model incorporating Eye Dynamics

1995-11-01
Kerry Emanuel
Numerical and theoretical models of tropical cyclones indicate that the maximum wind speed in mature storms is sensitive to the ratio of the enthalpy and momentum surface exchange coefficients and … Numerical and theoretical models of tropical cyclones indicate that the maximum wind speed in mature storms is sensitive to the ratio of the enthalpy and momentum surface exchange coefficients and that the spinup time of tropical cyclones varies inversely with the magnitude of these coefficients. At the same time, the Carnot cycle model developed by the author predicts that the central pressure of mature cyclones is independent of the magnitude of the exchange coefficients. The author presents numerical simulations that prove this last prediction false and suggest that the reason for this failure is the neglect of eye dynamics in the steady-state theory. On this basis, the existing theory is modified to account for eye dynamics, and the predictions of the revised theory are compared to the results of numerical simulations. Both the revised theory and the numerical modeling results, when compared to observations, suggest that the ratio of enthalpy to momentum exchange coefficients in real hurricanes lies in the range 0.75–1.5, contradicting published speculations about the behavior of this ratio at high surface wind speed.
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Atlantic hurricanes and natural variability in 2005

2006-06-01
Kevin E. Trenberth , Dennis J. Shea
The 2005 North Atlantic hurricane season (1 June to 30 November) was the most active on record by several measures, surpassing the very active season of 2004 and causing an … The 2005 North Atlantic hurricane season (1 June to 30 November) was the most active on record by several measures, surpassing the very active season of 2004 and causing an unprecedented level of damage. Sea surface temperatures (SSTs) in the tropical North Atlantic (TNA) region critical for hurricanes (10° to 20°N) were at record high levels in the extended summer (June to October) of 2005 at 0.9°C above the 1901–70 normal and were a major reason for the record hurricane season. Changes in TNA SSTs are associated with a pattern of natural variation known as the Atlantic Multi‐decadal Oscillation (AMO). However, previous AMO indices are conflated with linear trends and a revised AMO index accounts for between 0 and 0.1°C of the 2005 SST anomaly. About 0.45°C of the SST anomaly is common to global SST and is thus linked to global warming and, based on regression, about 0.2°C stemmed from after‐effects of the 2004–05 El Niño.
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The Recent Increase in Atlantic Hurricane Activity: Causes and Implications

2001-07-20
Stanley B. Goldenberg , Christopher W. Landsea , Alberto M. Mestas‐Nuñez +1 more
The years 1995 to 2000 experienced the highest level of North Atlantic hurricane activity in the reliable record. Compared with the generally low activity of the previous 24 years (1971 … The years 1995 to 2000 experienced the highest level of North Atlantic hurricane activity in the reliable record. Compared with the generally low activity of the previous 24 years (1971 to 1994), the past 6 years have seen a doubling of overall activity for the whole basin, a 2.5-fold increase in major hurricanes (≥50 meters per second), and a fivefold increase in hurricanes affecting the Caribbean. The greater activity results from simultaneous increases in North Atlantic sea-surface temperatures and decreases in vertical wind shear. Because these changes exhibit a multidecadal time scale, the present high level of hurricane activity is likely to persist for an additional ∼10 to 40 years. The shift in climate calls for a reevaluation of preparedness and mitigation strategies.

Downscaling CMIP5 climate models shows increased tropical cyclone activity over the 21st century

2013-07-08
Kerry Emanuel
A recently developed technique for simulating large [O(10(4))] numbers of tropical cyclones in climate states described by global gridded data is applied to simulations of historical and future climate states … A recently developed technique for simulating large [O(10(4))] numbers of tropical cyclones in climate states described by global gridded data is applied to simulations of historical and future climate states simulated by six Coupled Model Intercomparison Project 5 (CMIP5) global climate models. Tropical cyclones downscaled from the climate of the period 1950-2005 are compared with those of the 21st century in simulations that stipulate that the radiative forcing from greenhouse gases increases by over preindustrial values. In contrast to storms that appear explicitly in most global models, the frequency of downscaled tropical cyclones increases during the 21st century in most locations. The intensity of such storms, as measured by their maximum wind speeds, also increases, in agreement with previous results. Increases in tropical cyclone activity are most prominent in the western North Pacific, but are evident in other regions except for the southwestern Pacific. The increased frequency of events is consistent with increases in a genesis potential index based on monthly mean global model output. These results are compared and contrasted with other inferences concerning the effect of global warming on tropical cyclones.
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Upper Ocean Response to a Hurricane

1981-02-01
James F. Price
The upper ocean response to a moving hurricane is studied using historical air-sea data and a three-dimensional numerical ocean model. Sea surface temperature (SST) response is emphasized. The model has … The upper ocean response to a moving hurricane is studied using historical air-sea data and a three-dimensional numerical ocean model. Sea surface temperature (SST) response is emphasized. The model has a surface mixed-layer (ML) that entrains according to a velocity dependent parameterization, and two lower layers that simulate the response in the thermocline. The passage of Hurricane Eloise (1975) over buoy EB-10 is simulated in detail. SST decreased 2°C as Eloise passed directly over EB-10 at 8.5 m s−1. Model results indicate that entrainment caused 85% of the irreversible heat flux into the ML; air-sea heat exchange accounted for the remainder. The maximum SST response was predicted to be −3°C and to occur 60 km to the right of the hurricane track. This is consistent with the well-documented rightward bias in the SST response to rapidly moving hurricanes. The rightward bias occurs in the model solution because the hurricane wind-stress vector turns clockwise with time on the right side of the track and is roughly resonant with the ML velocity. High ML velocities cause strong entrainment and thus a strong SST response. Model comparisons with EB-10 data suggest that a wind-speed-dependent drag coefficient similar to Garratt's (1977) is appropriate for hurricane conditions. A constant drag coefficient 1.5 × 10−3 underpredicts the amplitude of upwelling and the SST response by ∼40%. Numerical experiments show that the response has a lively dependence on a number of air-sea parameters. Intense, slowly moving hurricanes cause the largest response. The SST response is largest where cold water is near the sea surface, i.e., where the initial ML is thin and the upper thermocline temperature gradient is sharp. Nonlocal processes are important to some aspects of the upper ocean response. Upwelling significantly enhances entrainment under slowly moving hurricanes (≲4 m s−1) and reduces the rightward bias of the SST response. Horizontal advection dominates the pointwise ML heat balance during the several-day period following a hurricane passage. Pressure gradients set up by the upwelling do not play an important role in the entrainment process, but are an effective mechanism for dispersing energy from the ML over a 5–10 day time scale.
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GLOBAL VIEW OF THE ORIGIN OF TROPICAL DISTURBANCES AND STORMS

1968-10-01
William M. Gray
A global observational study of atmospheric conditions associated with tropical disturbance and storm development is presented. This study primarily uses upper air observations which have become available over the tropical … A global observational study of atmospheric conditions associated with tropical disturbance and storm development is presented. This study primarily uses upper air observations which have become available over the tropical oceans in the last decade. Climatological values of vertical stability, low level wind, tropospheric vertical wind shear and other parameters relative to the location and seasons of tropical disturbance and storm development are discussed. Individual storm data are also presented in summary form for over 300 development cases (with over 1,500 individual observation times) for four tropical storm genesis areas. Results show that most tropical disturbances and storms form in regions equatorward of 20° lat. on the poleward side of doldrum Equatorial Troughs where the tropospheric vertical shear of horizontal wind (i.e., baroclinicity) is a minimum or zero. Storm development occurring on the poleward side of 20° lat. in the Northwest Atlantic and North-west Pacific takes place under significantly different environmental conditions, which are described. These latter developments make up but a small percentage of the global total. Observations are also presented which indicate that over the tropical oceans where disturbances and storms form, there is a distinct Ekman or frictional veering of the wind in the subcloud layer (surface to 600 m.) of approximately 10°. This produces or enhances synoptic-scale low level convergence and cumulus convection in regions of large positive relative vorticity which exist in the cyclonic wind shear areas surrounding doldrum Equatorial Troughs. Tropical disturbance and later storm development is viewed as primarily a result of large-scale Ekman or frictionally forced surface convergence (with resulting cumulus production and tropospheric heating), and a consequent inhibition of tropospheric ventilation by initially existing small vertical wind shear, and later inhibition of ventilation by cumulus up- and downdrafts acting to prevent increase of vertical shear as baroclinicity increases. The above processes produce the necessary condensation heating and allow for its concentration and containment in selective areas. Development is thus explained from a simple warming, hydrostatic adjustment point of view with the energy source analogous to Charney and Eliassen's proposed “conditional instability of the second kind.”
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Hurricanes and Global Warming: Results from Downscaling IPCC AR4 Simulations

2008-03-01
Kerry Emanuel , Ragoth Sundararajan , John K. Williams
Changes in tropical cyclone activity are among the more potentially consequential results of global climate change, and it is therefore of considerable interest to understand how anthropogenic climate change may … Changes in tropical cyclone activity are among the more potentially consequential results of global climate change, and it is therefore of considerable interest to understand how anthropogenic climate change may affect such storms. Global climate models are currently used to estimate future climate change, but the current generation of models lacks the horizontal resolution necessary to resolve the intense inner core of tropical cyclones. Here we review a new technique for inferring tropical cyclone climatology from the output of global models, extend it to predict genesis climatologies (rather than relying on historical climatology), and apply it to current and future climate states simulated by a suite of global models developed in support of the most recent Intergovernmental Panel on Climate Change report. This new technique attacks the horizontal resolution problem by using a specialized, coupled ocean-atmosphere hurricane model phrased in angular momentum coordinates, which provide a high resolution of the core at low cost. This model is run along each of 2,000 storm tracks generated using an advection-and-beta model, which is, in turn, driven by large-scale winds derived from the global models. In an extension to this method, tracks are initiated by randomly seeding large areas of the tropics with weak vortices and then allowing the intensity model to determine their survival, based on large-scale environmental conditions. We show that this method is largely successful in reproducing the observed seasonal cycle and interannual variability of tropical cyclones in the present climate, and that it is more modestly successful in simulating their spatial distribution. When applied to simulations of global climate with double the present concentration of carbon dioxide, this method predicts substantial changes and geographic shifts in tropical cyclone activity, but with much variation among the global climate models used. Basinwide power dissipation and storm intensity generally increase with global warming, but the results vary from model to model and from basin to basin. Storm frequency decreases in the Southern Hemisphere and north Indian Ocean, increases in the western North Pacific, and is indeterminate elsewhere. We demonstrate that in these simulations, the change in tropical cyclone activity is greatly influenced by the increasing difference between the moist entropy of the boundary layer and that of the middle troposphere as the climate warms.
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How Strong ENSO Events Affect Tropical Storm Activity over the Western North Pacific*

2002-07-01
Bin Wang , Johnny C. L. Chan
An analysis of 35-yr (1965–99) data reveals vital impacts of strong (but not moderate) El Niño and La Niña events on tropical storm (TS) activity over the western North Pacific … An analysis of 35-yr (1965–99) data reveals vital impacts of strong (but not moderate) El Niño and La Niña events on tropical storm (TS) activity over the western North Pacific (WNP). Although the total number of TSs formed in the entire WNP does not vary significantly from year to year, during El Niño summer and fall, the frequency of TS formation increases remarkably in the southeast quadrant (0°–17°N, 140°E–180°) and decreases in the northwest quadrant (17°–30°N, 120°–140°E). The July–September mean location of TS formation is 6° latitude lower, while that in October–December is 18° longitude eastward in the strong warm versus strong cold years. After the El Niño (La Niña), the early season (January–July) TS formation in the entire WNP is suppressed (enhanced). In strong warm (cold) years, the mean TS life span is about 7 (4) days, and the mean number of days of TS occurrence is 159 (84) days. During the fall of strong warm years, the number of TSs, which recurve northward across 35°N, is 2.5 times more than during strong cold years. This implies that El Niño substantially enhances poleward transport of heat–moisture and impacts high latitudes through changing TS formation and tracks. The enhanced TS formation in the SE quadrant is attributed to the increase of the low-level shear vorticity generated by El Niño–induced equatorial westerlies, while the suppressed TS generation over the NW quadrant is ascribed to upper-level convergence induced by the deepening of the east Asian trough and strengthening of the WNP subtropical high, both resulting from El Niño forcing. The WNP TS activities in July–December are noticeably predictable using preceding winter–spring Niño-3.4 SST anomalies, while the TS formation in March–July is exceedingly predictable using preceding October–December Niño-3.4 SST anomalies. The physical basis for the former is the phase lock of ENSO evolution to the annual cycle, while for the latter it is the persistence of Philippine Sea wind anomalies that are excited by ENSO forcing but maintained by local atmosphere–ocean interaction.
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Reduced drag coefficient for high wind speeds in tropical cyclones

2003-03-01
Mark D. Powell , Peter J. Vickery , Timothy A. Reinhold

Stratiform Precipitation in Regions of Convection: A Meteorological Paradox?

1997-10-01
Robert A. Houze
It was once generally thought that stratiform precipitation was something occurring primarily, if not exclusively, in middle latitudes—in baroclinic cyclones and fronts. Early radar observations in the Tropics, however, showed … It was once generally thought that stratiform precipitation was something occurring primarily, if not exclusively, in middle latitudes—in baroclinic cyclones and fronts. Early radar observations in the Tropics, however, showed large radar echoes composed of convective rain alongside stratiform precipitation, with the stratiform echoes covering great areas and accounting for a large portion of the tropical rainfall. These observations seemed paradoxical, since stratiform precipitation should not have been occurring in the Tropics, where baroclinic cyclones do not occur. Instead it was falling from convection-generated clouds, generally thought to be too violent to be compatible with the layered, gently settling behavior of stratiform precipitation. In meteorology, convection is a dynamic concept; specifically, it is the rapid, efficient, vigorous overturning of the atmosphere required to neutralize an unstable vertical distribution of moist static energy. Most clouds in the Tropics are convection-generated cumulonimbus. These cumulonimbus clouds contain an evolving pattern of newer and older precipitation. The young portions of the cumulonimbus are too violent to produce stratiform precipitation. In young, vigorous convective regions of the cumulonimbus, precipitation particles increase their mass by collection of cloud water, and the particles fall out in heavy showers, which appear on radar as vertically oriented convective "cells." In regions of older convection, however, the vertical air motions are generally weaker, and the precipitation particles drift downward, with the particles increasing their mass by vapor diffusion. In these regions the radar echoes are stratiform, and typically these echoes occur adjacent to regions of younger convective showers. Thus, the stratiform and convective precipitation both occur within the same complex of convection-generated cumulonimbus cloud. The feedbacks of the apparent heat source and moisture sink of tropical cumulonimbus convection to the large-scale dynamics of the atmosphere are distinctly separable by precipitation region. The part of the atmospheric response deriving from the areas of young, vigorous convective cells is two layered, with air converging into the active convection at low levels and diverging aloft. The older, weaker intermediary and stratiform precipitation areas induce a three-layered response, in which environmental air converges into the weak precipitation area at midlevels and diverges from it at lower and upper levels. If global precipitation data, such as that to be provided by the Tropical Rainfall Measuring Mission, are to be used to validate the heating patterns predicted by climate and general circulation models, algorithms must be applied to the precipitation data that will identify the two principal modes of heating, by separating the convective component of the precipitation from the remainder.
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Convectively coupled equatorial waves

2009-04-09
George N. Kiladis , Matthew C. Wheeler , Patrick T. Haertel +2 more
Convectively coupled equatorial waves (CCEWs) control a substantial fraction of tropical rainfall variability. Their horizontal structures and dispersion characteristics correspond to Matsuno's (1966) solutions of the shallow water equations on … Convectively coupled equatorial waves (CCEWs) control a substantial fraction of tropical rainfall variability. Their horizontal structures and dispersion characteristics correspond to Matsuno's (1966) solutions of the shallow water equations on an equatorial beta plane, namely, Kelvin, equatorial Rossby, mixed Rossby‐gravity, and inertio‐gravity waves. Because of moist processes, the tilted vertical structures of CCEWs are complex, and their scales do not correspond to that expected from the linear theory of dry waves. The dynamical structures and cloud morphology of CCEWs display a large degree of self‐similarity over a surprisingly wide range of scales, with shallow convection at their leading edge, followed by deep convection and then stratiform precipitation, mirroring that of individual mesoscale convective complexes. CCEWs have broad impacts within the tropics, and their simulation in general circulation models is still problematic, although progress has been made using simpler models. A complete understanding of CCEWs remains a challenge in tropical meteorology.
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RAMS 2001: Current status and future directions

2003-01-01
William R. Cotton , Roger A. Pielke , R. L. Walko +7 more

Atlantic Seasonal Hurricane Frequency. Part I: El Niño and 30 mb Quasi-Biennial Oscillation Influences

1984-09-01
William M. Gray
This is the first of two papers on Atlantic seasonal hurricane frequency. In this paper, seasonal hurricane frequency as related to E1 Niño events during 1900–82 and to the equatorial … This is the first of two papers on Atlantic seasonal hurricane frequency. In this paper, seasonal hurricane frequency as related to E1 Niño events during 1900–82 and to the equatorial Quasi-Biennial Oscillation (QBO) of stratospheric zonal wind from 1950 to 1982 is discussed. It is shown that a substantial negative correlation is typically present between the seasonal number of hurricanes, hurricane days and tropical storms, and moderate or strong (15 cases) El Niñ off the South American west coast. A similar negative anomaly in hurricane activity occurs when equatorial winds at 30 mb are from an easterly direction and/or are becoming more easterly with time during the hurricane season. This association of Atlantic hurricane activity with El Niño can also be made with the Southern Oscillation Index. By contrast, seasonal hurricane frequency is slightly above normal in non-El Niño years and substantially above normal when equatorial stratospheric winds blow from a westerly direction and/or are becoming more westerly with time during the storm season. El Niño events are shown to be related to an anomalous increase in upper tropospheric westerly winds over the Caribbean basin and the equatorial Atlantic. Such anomalous westerly winds inhibit tropical cyclone activity by increasing tropospheric vertical wind shear and giving rise to a regional upper-level environment which is less anticyclonic and consequently less conductive to cyclone development and maintenance. The seasonal frequency of hurricane activity in storm basis elsewhere is much less affected by El Niño events and the QBO. Seasonal hurricane frequency in the Atlantic and the stratospheric QBO is hypothesized to be associated with the trade-wind nature of Atlantic cyclone formation. Tropical cyclone formation in the other storm basins is primarily associated with monsoon trough conditions which are absent in the Atlantic. Quasi-Biennial Oscillation-induced influences do not positively enhance monsoon trough region vorticity fields as they apparently do with cyclone formations within the trade winds. Part II discusses the utilization of the information in this paper for the development of a forecast scheme for seasonal hurricane activity variations.
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Increasing destructiveness of tropical cyclones over the past 30 years

2005-07-31
Kerry Emanuel

On the Growth of the Hurricane Depression

1964-01-01
J. G. Charney , Arnt Eliassen
Why do cyclones form in a conditionally unstable tropical atmosphere whose vertical thermal structure is apparently more favorable to small-scale cumulus convection than to convective circulations of tropical cyclone scale? … Why do cyclones form in a conditionally unstable tropical atmosphere whose vertical thermal structure is apparently more favorable to small-scale cumulus convection than to convective circulations of tropical cyclone scale? It is proposed that the cyclone develops by a kind of secondary instability in which existing cumulus convection is augmented in regions of low-level horizontal convergence and quenched in regions of low-level divergence. The cumulus- and cyclone-scale motions are thus to be regarded as cooperating rather than as competing–the clouds supplying latent heat energy to the cyclone, and the cyclone supplying the fuel, in the form of moisture, to the clouds. A scale-analysis indicates that it is appropriate to use the balance equations of Eliassen for the macro-motion; in this case the effect of friction in the boundary-layer may be incorporated as a condition on the vertical velocity at the top of the boundary layer. It is argued that the mean humidity in a system of convecting cumulus clouds in statistical equilibrium with the cyclone-scale circulation is appreciably less than its saturation value. The atmosphere is then gravitationally stable for the macro-scale convective process even though it is gravitationally unstable for the micro-scale convective process. The amplification of the disturbance is due to the surface frictionally induced convergence of moisture and liberation of latent heat in the center of the cyclone.
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The dependence of hurricane intensity on climate

1987-04-01
Kerry Emanuel

The Dependence of Numerically Simulated Convective Storms on Vertical Wind Shear and Buoyancy

1982-06-01
Morris L. Weisman , Joseph B. Klemp
The effects of vertical wind shear and buoyancy on convective storm structure and evolution are investigated with the use of a three-dimensional numerical cloud model. By varying the magnitude of … The effects of vertical wind shear and buoyancy on convective storm structure and evolution are investigated with the use of a three-dimensional numerical cloud model. By varying the magnitude of buoyant energy and one-directional vertical shear over a wide range of environmental conditions associated with severe storms, the model is able to produce a spectrum of storm types qualitatively similar to those observed in nature. These include short-lived single cells, certain types of multicells and rotating supercells. The relationship between wind shear and buoyancy is expressed in terms of a nondimensional convective parameter which delineates various regimes of storm structure and, in particular, suggests optimal conditions for the development of supercell type storms. Applications of this parameter to well-documented severe storm cases agree favorably with the model results, suggesting both the value of the model in studying these modes of convection as well as the value of this representation in identifying the proper environment for the development of various storm types.
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Orographic effects on precipitating clouds

2011-09-16
Robert A. Houze
Precipitation over and near mountains is not caused by topography but, rather, occurs when storms of a type that can occur anywhere (deep convection, fronts, tropical cyclones) form near or … Precipitation over and near mountains is not caused by topography but, rather, occurs when storms of a type that can occur anywhere (deep convection, fronts, tropical cyclones) form near or move over complex terrain. Deep convective systems occurring near mountains are affected by channeling of airflow near mountains, capping of moist boundary layers by flow subsiding from higher terrain, and triggering to break the cap when low‐level flow encounters hills near the bases of major mountain ranges. Mesoscale convective systems are triggered by nocturnal downslope flows and by diurnally triggered disturbances propagating away from mountain ranges. The stratiform regions of mesoscale convective systems are enhanced by upslope flow when they move over mountains. In frontal cloud systems, the poleward flow of warm‐sector air ahead of the system may rise easily over terrain, and a maximum of precipitating cloud occurs over the first rise of terrain, and rainfall is maximum on ridges and minimum in valleys. If the low‐level air ahead of the system is stable, blocking or damming occurs. Shear between a blocked layer and unblocked moist air above favors turbulent overturning, which can accelerate precipitation fallout. In tropical cyclones, the tangential winds encountering a mountain range produce a gravity wave response and greatly enhanced upslope flow. Depending on the height of the mountain, the maximum rain may occur on either the windward or leeward side. When the capped boundary layer of the eye of a tropical cyclone passes over a mountain, the cap may be broken with intense convection resulting.
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The impacts of climate change on the risk of natural disasters

2006-03-01
Maarten van Aalst
Human emissions of greenhouse gases are already changing our climate. This paper provides an overview of the relation between climate change and weather extremes, and examines three specific cases where … Human emissions of greenhouse gases are already changing our climate. This paper provides an overview of the relation between climate change and weather extremes, and examines three specific cases where recent acute events have stimulated debate on the potential role of climate change: the European heatwave of 2003; the risk of inland flooding, such as recently in Central Europe and Great Britain; and the harsh Atlantic hurricane seasons of 2004 and 2005. Furthermore, it briefly assesses the relation between climate change and El Niño, and the potential of abrupt climate change. Several trends in weather extremes are sufficiently clear to inform risk reduction efforts. In many instances, however, the potential increases in extreme events due to climate change come on top of alarming rises in vulnerability. Hence, the additional risks due to climate change should not be analysed or treated in isolation, but instead integrated into broader efforts to reduce the risk of natural disasters.

On the limiting aerodynamic roughness of the ocean in very strong winds

2004-09-01
Mark A. Donelan , Brian K. Haus , Nicolás Reul +5 more
The aerodynamic friction between air and sea is an important part of the momentum balance in the development of tropical cyclones. Measurements of the drag coefficient, relating the tangential stress … The aerodynamic friction between air and sea is an important part of the momentum balance in the development of tropical cyclones. Measurements of the drag coefficient, relating the tangential stress (frictional drag) between wind and water to the wind speed and air density, have yielded reliable information in wind speeds less than 20 m/s (about 39 knots). In these moderate conditions it is generally accepted that the drag coefficient (or equivalently, the “aerodynamic roughness”) increases with the wind speed. Can one merely extrapolate this wind speed tendency to describe the aerodynamic roughness of the ocean in the extreme wind speeds that occur in hurricanes (wind speeds greater than 30 m/s)? This paper attempts to answer this question, guided by laboratory extreme wind experiments, and concludes that the aerodynamic roughness approaches a limiting value in high winds. A fluid mechanical explanation of this phenomenon is given.
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Convectively Coupled Equatorial Waves: Analysis of Clouds and Temperature in the Wavenumber–Frequency Domain

1999-02-01
Matthew C. Wheeler , George N. Kiladis
A wavenumber-frequency spectrum analysis is performed for all longitudes in the domain 15°S–15°N using a long (∼18 years) twice-daily record of satellite-observed outgoing longwave radiation (OLR), a good proxy for … A wavenumber-frequency spectrum analysis is performed for all longitudes in the domain 15°S–15°N using a long (∼18 years) twice-daily record of satellite-observed outgoing longwave radiation (OLR), a good proxy for deep tropical convection. The broad nature of the spectrum is red in both zonal wavenumber and frequency. By removing an estimated background spectrum, numerous statistically significant spectral peaks are isolated. Some of the peaks correspond quite well to the dispersion relations of the equatorially trapped wave modes of shallow water theory with implied equivalent depths in the range of 12–50 m. Cross-spectrum analysis with the satellite-based microwave sounding unit deep-layer temperature data shows that these spectral peaks in the OLR are “coupled” with this dynamical field. The equivalent depths of the convectively coupled waves are shallower than those typical of equatorial waves uncoupled with convection. Such a small equivalent depth is thought to be a result of the interaction between convection and the dynamics. The convectively coupled equatorial waves identified correspond to the Kelvin, n = 1 equatorial Rossby, mixed Rossby-gravity, n = 0 eastward inertio-gravity, n = 1 westward inertio-gravity (WIG), and n = 2 WIG waves. Additionally, the Madden–Julian oscillation and tropical depression-type disturbances are present in the OLR spectra. These latter two features are unlike the convectively coupled equatorial waves due to their location away from the equatorial wave dispersion curves in the wavenumber-frequency domain. Extraction of the different convectively coupled disturbances in the time–longitude domain is performed by filtering the OLR dataset for very specific zonal wavenumbers and frequencies. The geographical distribution of the variance of these filtered data gives further evidence that some of the spectral peaks correspond to particular equatorial wave modes. The results have implications for the cumulus parameterization problem, for the excitation of equatorial waves in the lower stratosphere, and for extended-range forecasting in the Tropics.
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Impact of Atlantic multidecadal oscillations on India/Sahel rainfall and Atlantic hurricanes

2006-09-01
Rong Zhang , Thomas L. Delworth
Prominent multidecadal fluctuations of India summer rainfall, Sahel summer rainfall, and Atlantic Hurricane activity have been observed during the 20th century. Understanding their mechanism(s) will have enormous social and economic … Prominent multidecadal fluctuations of India summer rainfall, Sahel summer rainfall, and Atlantic Hurricane activity have been observed during the 20th century. Understanding their mechanism(s) will have enormous social and economic implications. We first use statistical analyses to show that these climate phenomena are coherently linked. Next, we use the GFDL CM2.1 climate model to show that the multidecadal variability in the Atlantic ocean can cause the observed multidecadal variations of India summer rainfall, Sahel summer rainfall and Atlantic Hurricane activity (as inferred from vertical wind shear changes). These results suggest that to interpret recent climate change we cannot ignore the important role of Atlantic multidecadal variability.

Normalized Hurricane Damage in the United States: 1900–2005

2008-01-18
Roger A. Pielke , Joel Gratz , Christopher W. Landsea +3 more
After more than two decades of relatively little Atlantic hurricane activity, the past decade saw heightened hurricane activity and more than $150 billion in damage in 2004 and 2005. This … After more than two decades of relatively little Atlantic hurricane activity, the past decade saw heightened hurricane activity and more than $150 billion in damage in 2004 and 2005. This paper normalizes mainland U.S. hurricane damage from 1900–2005 to 2005 values using two methodologies. A normalization provides an estimate of the damage that would occur if storms from the past made landfall under another year’s societal conditions. Our methods use changes in inflation and wealth at the national level and changes in population and housing units at the coastal county level. Across both normalization methods, there is no remaining trend of increasing absolute damage in the data set, which follows the lack of trends in landfall frequency or intensity observed over the twentieth century. The 1970s and 1980s were notable because of the extremely low amounts of damage compared to other decades. The decade 1996–2005 has the second most damage among the past 11 decades, with only the decade 1926–1935 surpassing its costs. Over the 106years of record, the average annual normalized damage in the continental United States is about $10 billion under both methods. The most damaging single storm is the 1926 Great Miami storm, with $140–157 billion of normalized damage: the most damaging years are 1926 and 2005. Of the total damage, about 85% is accounted for by the intense hurricanes (Saffir-Simpson Categories 3, 4, and 5), yet these have comprised only 24% of the U.S. landfalling tropical cyclones. Unless action is taken to address the growing concentration of people and properties in coastal areas where hurricanes strike, damage will increase, and by a great deal, as more and wealthier people increasingly inhabit these coastal locations.

Coastal flood damage and adaptation costs under 21st century sea-level rise

2014-02-03
Jochen Hinkel , Daniël Lincke , Athanasios T. Vafeidis +7 more
Coastal flood damage and adaptation costs under 21st century sea-level rise are assessed on a global scale taking into account a wide range of uncertainties in continental topography data, population … Coastal flood damage and adaptation costs under 21st century sea-level rise are assessed on a global scale taking into account a wide range of uncertainties in continental topography data, population data, protection strategies, socioeconomic development and sea-level rise. Uncertainty in global mean and regional sea level was derived from four different climate models from the Coupled Model Intercomparison Project Phase 5, each combined with three land-ice scenarios based on the published range of contributions from ice sheets and glaciers. Without adaptation, 0.2-4.6% of global population is expected to be flooded annually in 2100 under 25-123 cm of global mean sea-level rise, with expected annual losses of 0.3-9.3% of global gross domestic product. Damages of this magnitude are very unlikely to be tolerated by society and adaptation will be widespread. The global costs of protecting the coast with dikes are significant with annual investment and maintenance costs of US$ 12-71 billion in 2100, but much smaller than the global cost of avoided damages even without accounting for indirect costs of damage to regional production supply. Flood damages by the end of this century are much more sensitive to the applied protection strategy than to variations in climate and socioeconomic scenarios as well as in physical data sources (topography and climate model). Our results emphasize the central role of long-term coastal adaptation strategies. These should also take into account that protecting large parts of the developed coast increases the risk of catastrophic consequences in the case of defense failure.
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Restoration of the Mississippi Delta: Lessons from Hurricanes Katrina and Rita

2007-03-22
John W. Day , Donald F. Boesch , Ellis J. Clairain +7 more
Hurricanes Katrina and Rita showed the vulnerability of coastal communities and how human activities that caused deterioration of the Mississippi Deltaic Plain (MDP) exacerbated this vulnerability. The MDP formed by … Hurricanes Katrina and Rita showed the vulnerability of coastal communities and how human activities that caused deterioration of the Mississippi Deltaic Plain (MDP) exacerbated this vulnerability. The MDP formed by dynamic interactions between river and coast at various temporal and spatial scales, and human activity has reduced these interactions at all scales. Restoration efforts aim to re-establish this dynamic interaction, with emphasis on reconnecting the river to the deltaic plain. Science must guide MDP restoration, which will provide insights into delta restoration elsewhere and generally into coasts facing climate change in times of resource scarcity.

An Overview of the China Meteorological Administration Tropical Cyclone Database

2013-07-22
Ming Ying , Wei Zhang , Hui Yu +5 more
The China Meteorological Administration (CMA)’s tropical cyclone (TC) database includes not only the best-track dataset but also TC-induced wind and precipitation data. This article summarizes the characteristics and key technical … The China Meteorological Administration (CMA)’s tropical cyclone (TC) database includes not only the best-track dataset but also TC-induced wind and precipitation data. This article summarizes the characteristics and key technical details of the CMA TC database. In addition to the best-track data, other phenomena that occurred with the TCs are also recorded in the dataset, such as the subcenters, extratropical transitions, outer-range severe winds associated with TCs over the South China Sea, and coastal severe winds associated with TCs landfalling in China. These data provide additional information for researchers. The TC-induced wind and precipitation data, which map the distribution of severe wind and rainfall, are also helpful for investigating the impacts of TCs. The study also considers the changing reliability of the various data sources used since the database was created and the potential causes of temporal and spatial inhomogeneities within the datasets. Because of the greater number of observations available for analysis, the CMA TC database is likely to be more accurate and complete over the offshore and land areas of China than over the open ocean. Temporal inhomogeneities were induced primarily by changes to the nature and quality of the input data, such as the development of a weather observation network in China and the use of satellite image analysis to replace the original aircraft reconnaissance data. Furthermore, technical and factitious changes, such as to the wind–pressure relationship and the satellite-derived current intensity (CI) number–intensity conversion, also led to inhomogeneities within the datasets.
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Atmospheric Rivers, Floods and the Water Resources of California

2011-03-24
Michael D. Dettinger , F. Martin Ralph , Tapash Das +2 more
California’s highly variable climate and growing water demands combine to pose both water-supply and flood-hazard challenges to resource managers. Recently important efforts to more fully integrate the management of floods … California’s highly variable climate and growing water demands combine to pose both water-supply and flood-hazard challenges to resource managers. Recently important efforts to more fully integrate the management of floods and water resources have begun, with the aim of benefitting both sectors. California is shown here to experience unusually large variations in annual precipitation and streamflow totals relative to the rest of the US, variations which mostly reflect the unusually small average number of wet days per year needed to accumulate most of its annual precipitation totals (ranging from 5 to 15 days in California). Thus whether just a few large storms arrive or fail to arrive in California can be the difference between a banner year and a drought. Furthermore California receives some of the largest 3-day storm totals in the country, rivaling in this regard the hurricane belt of the southeastern US. California’s largest storms are generally fueled by landfalling atmospheric rivers (ARs). The fractions of precipitation and streamflow totals at stations across the US that are associated with ARs are documented here and, in California, contribute 20–50% of the state’s precipitation and streamflow. Prospects for long-lead forecasts of these fractions are presented. From a meteorological perspective, California’s water resources and floods are shown to derive from the same storms to an extent that makes integrated flood and water resources management all the more important.
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Development of a Coupled Ocean–Atmosphere–Wave–Sediment Transport (COAWST) Modeling System

2010-01-01
John C. Warner , Brandy Armstrong , Ruoying He +1 more
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Effects of a Warm Oceanic Feature on Hurricane Opal

2000-05-01
Lynn K. Shay , Gustavo Goñi , Peter G. Black
On 4 October 1995, Hurricane Opal deepened from 965 to 916 hPa in the Gulf of Mexico over a 14-h period upon encountering a warm core ring (WCR) in the … On 4 October 1995, Hurricane Opal deepened from 965 to 916 hPa in the Gulf of Mexico over a 14-h period upon encountering a warm core ring (WCR) in the ocean shed by the Loop Current during an upper-level atmospheric trough interaction. Based on historical hydrographic measurements placed within the context of a two-layer model and surface height anomalies (SHA) from the radar altimeter on the TOPEX mission, upper-layer thickness fields indicated the presence of two warm core rings during September and October 1995. As Hurricane Opal passed directly over one of these WCRs, the 1-min surface winds increased from 35 to more than 60 m s−1, and the radius of maximum wind decreased from 40 to 25 km. Pre-Opal SHAs in the WCR exceeded 30 cm where the estimated depth of the 20°C isotherm was located between 175 and 200 m. Subsequent to Opal’s passage, this depth decreased approximately 50 m, which suggests upwelling underneath the storm track due to Ekman divergence. The maximum heat loss of approximately 24 Kcal cm−2 relative to depth of the 26°C isotherm was a factor of 6 times the threshold value required to sustain a hurricane. Since most of this loss occurred over a period of 14 h, the heat content loss of 24 Kcal cm−2 equates to approximately 20 kW m−2. Previous observational findings suggest that about 10%–15% of upper-ocean cooling is due to surface heat fluxes. Estimated surface heat fluxes based upon heat content changes range from 2000 to 3000 W m−2 in accord with numerically simulated surface heat fluxes during Opal’s encounter with the WCR. Composited AVHRR-derived SSTs indicated a 2°–3°C cooling associated with vertical mixing in the along-track direction of Opal except over the WCR where AVHRR-derived and buoy-derived SSTs decreased only by about 0.5°–1°C. Thus, the WCR’s effect was to provide a regime of positive feedback to the hurricane rather than negative feedback induced by cooler waters due to upwelling and vertical mixing as observed over the Bay of Campeche and north of the WCR.

The impact of climate change on global tropical cyclone damage

2012-01-13
Robert Mendelsohn , Kerry Emanuel , Shun Chonabayashi +1 more

Changes in Tropical Cyclone Number, Duration, and Intensity in a Warming Environment

2005-09-15
Peter J. Webster , Greg J. Holland , Judith A. Curry +1 more
We examined the number of tropical cyclones and cyclone days as well as tropical cyclone intensity over the past 35 years, in an environment of increasing sea surface temperature. A … We examined the number of tropical cyclones and cyclone days as well as tropical cyclone intensity over the past 35 years, in an environment of increasing sea surface temperature. A large increase was seen in the number and proportion of hurricanes reaching categories 4 and 5. The largest increase occurred in the North Pacific, Indian, and Southwest Pacific Oceans, and the smallest percentage increase occurred in the North Atlantic Ocean. These increases have taken place while the number of cyclones and cyclone days has decreased in all basins except the North Atlantic during the past decade.

A lateral boundary formulation for multi‐level prediction models

1976-04-01
Huw C. Davies
Abstract An expedient method is proposed for the lateral boundary treatment of a limited‐area prediction model. The method involves the relaxation of the interior flow in the vicinity of the … Abstract An expedient method is proposed for the lateral boundary treatment of a limited‐area prediction model. The method involves the relaxation of the interior flow in the vicinity of the boundary to the external fully prescribed flow. A systematic study of the method is undertaken with an (x, z) , linear, primitive equation model. Analytical considerations of the method for the continuous equations demonstrate the manner in which the method consumes gravity wave energy, error and fine spatial scale potential vorticity near the lateral boundaries. Numerical experiments are also undertaken to assess the usefulness of the method. The results indicate that the method gives an adequate representation of outgoing gravity waves with and without an ambient shear flow, and also allows the substantially undistorted transmission of geostrophically balanced flow out of the interior of the limited domain. On the basis of these results, it is suggested that the method constitutes a promising utilitarian treatment of the lateral boundaries.

Tropical cyclones and climate change

2010-02-21
Thomas R. Knutson , John L. McBride , Johnny C. L. Chan +7 more
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On the use and significance of isentropic potential vorticity maps

1985-10-01
Brian J. Hoskins , M. E. McIntyre , Andrew W. Robertson
Abstract The two main principles underlying the use of isentropic maps of potential vorticity to represent dynamical processes in the atmosphere are reviewed, including the extension of those principles to … Abstract The two main principles underlying the use of isentropic maps of potential vorticity to represent dynamical processes in the atmosphere are reviewed, including the extension of those principles to take the lower boundary condition into account. the first is the familiar Lagrangian conservation principle, for potential vorticity (PV) and potential temperature, which holds approximately when advective processes dominate frictional and diabatic ones. the second is the principle of ‘invertibility’ of the PV distribution, which holds whether or not diabatic and frictional processes are important. the invertibility principle states that if the total mass under each isentropic surface is specified, then a knowledge of the global distribution of PV on each isentropic surface and of potential temperature at the lower boundary (which within certain limitations can be considered to be part of the PV distribution) is sufficient to deduce, diagnostically, all the other dynamical fields, such as winds, temperatures, geopotential heights, static stabilities, and vertical velocities, under a suitable balance condition. the statement that vertical velocities can be deduced is related to the well‐known omega equation principle, and depends on having sufficient information about diabatic and frictional processes. Quasi‐geostrophic, semigeostrophic, and ‘nonlinear normal mode initialization’ realizations of the balance condition are discussed. an important constraint on the mass‐weighted integral of PV over a material volume and on its possible diabatic and frictional change is noted. Some basic examples are given, both from operational weather analyses and from idealized theoretical models, to illustrate the insights that can be gained from this approach and to indicate its relation to classical synoptic and air‐mass concepts. Included are discussions of (a) the structure, origin and persistence of cutoff cyclones and blocking anticyclones, (b) the physical mechanisms of Rossby wave propagation, baroclinic instability, and barotropic instability, and (c) the spatially and temporally nonuniform way in which such waves and instabilities may become strongly nonlinear, as in an occluding cyclone or in the formation of an upper air shear line. Connections with principles derived from synoptic experience are indicated, such as the ‘PVA rule’ concerning positive vorticity advection on upper air charts, and the role of disturbances of upper air origin, in combination with low‐level warm advection, in triggering latent heat release to produce explosive cyclonic development. In all cases it is found that time sequences of isentropic potential vorticity and surface potential temperature charts—which succinctly summarize the combined effects of vorticity advection, thermal advection, and vertical motion without requiring explicit knowledge of the vertical motion field—lead to a very clear and complete picture of the dynamics. This picture is remarkably simple in many cases of real meteorological interest. It involves, in principle, no sacrifices in quantitative accuracy beyond what is inherent in the concept of balance, as used for instance in the initialization of numerical weather forecasts.
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A Nonhydrostatic Version of the Penn State–NCAR Mesoscale Model: Validation Tests and Simulation of an Atlantic Cyclone and Cold Front

1993-05-01
Jimy Dudhia
A nonhydrostatic extension to the Pennsylvania State University-NCAR Mesoscale Model is presented. This new version employs reference pressure as the basis for a terrain-following vertical coordinate and the fully compressible … A nonhydrostatic extension to the Pennsylvania State University-NCAR Mesoscale Model is presented. This new version employs reference pressure as the basis for a terrain-following vertical coordinate and the fully compressible system of equations. In combination with the existing initialization techniques and physics of the current hydrostatic model, this provides a model capable of real-data simulations on any scale, limited only by data resolution and quality and by computer resources. The model uses pressure perturbation and temperature as prognostic variables as well as a B-grid staggering in contrast to most current nonhydrostatic models. The compressible equations are solved with a split-time- step approach where sound waves are treated semi-implicitly on the shorter step. Numerical techniques and finite differencing are described. Two-dimensional tests of flow over a bell-shaped hill on a range of scales were carded out with the hydrostatic and nonhydrostatic models to contrast the two and to verify the dynamics of the new version. Several three-dimensional real-data simulations show the potential use of grid-nesting applications whereby the model is initialized from a coarser hydrostatic or nonhydrostatic model output by interpolation to a smaller grid area of typically between two and four times finer resolution. This approach is illustrated by a simulation of a cold front within a developing midlatitude cyclone, and a comparison of the front to observations of similar features. The cold-frontal boundary was sharply defined at low levels and consisted of narrow linear updraft cores. At 2–4-km altitude this structure gave way to a more diffuse boundary with apparent mixing. Mechanisms are presented to explain these features in terms of inertial and shearing instability. Convection embedded in the frontal band formed a prefrontal line at later stages. Finally, sensitivity studies showed that the frontal band owed its narrowness to the concentrating effect of latent heating. The frontal ascending branch was supplied by a strong easterly ageostrophic flow in the warm sector.
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An Analytic Model of the Wind and Pressure Profiles in Hurricanes

1980-08-01
Greg J. Holland
Abstract An analytic model of the radial profiles of sea level pressure and winds in a hurricane is presented. The equations contain two parameters which may be empirically estimated from … Abstract An analytic model of the radial profiles of sea level pressure and winds in a hurricane is presented. The equations contain two parameters which may be empirically estimated from observations in a hurricane or determined climatologically to define a standard hurricane; example are given. The model is shown to be generally superior to two other widely used models and is considered to be a valuable aid in operational forecasting, case studies and engineering work.

An Air-Sea Interaction Theory for Tropical Cyclones. Part I: Steady-State Maintenance

1986-03-01
Kerry Emanuel
Observations and numerical simulators of tropical cyclones show that evaporation from the sea surface is essential to the development of reasonably intense storms. On the other hand, the CISK hypothesis, … Observations and numerical simulators of tropical cyclones show that evaporation from the sea surface is essential to the development of reasonably intense storms. On the other hand, the CISK hypothesis, in the form originally advanced by Charney and Eliassen, holds that initial development results from the organized release of preexisting conditional instability. In this series of papers, we explore the relative importance of ambient conditional instability and air-sea latent and sensible heat transfer in both the development and maintenance of tropical cyclones using highly idealized models. In particular, we advance the hypothesis that the intensification and maintenance of tropical cyclones depend exclusively on self-induced heat transfer from the ocean. In this sense, these storms may be regarded as resulting from a finite amplitude air-sea interaction instability rather than from a linear instability involving ambient potential buoyancy. In the present paper, we attempt to show that reasonably intense cyclones may be maintained in a steady state without conditional instability of ambient air. In Part II we will demonstrate that weak but finite-amplitude axisymmetric disturbances may intensify in a conditionally neutral environment.
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Increasing risk of compound flooding from storm surge and rainfall for major US cities

2015-07-27
Thomas Wahl , Shaleen Jain , Jens Bender +2 more

Tropical Cyclones and Climate Change Assessment: Part II: Projected Response to Anthropogenic Warming

2019-08-06
Thomas R. Knutson , Suzana J. Camargo , Johnny C. L. Chan +7 more
<section class="abstract"><h2 class="abstractTitle text-title my-1" id="d13860437e169">Abstract</h2> Model projections of tropical cyclone (TC) activity response to anthropogenic warming in climate models are assessed. Observations, theory, and models, with increasing robustness, indicate … <section class="abstract"><h2 class="abstractTitle text-title my-1" id="d13860437e169">Abstract</h2> Model projections of tropical cyclone (TC) activity response to anthropogenic warming in climate models are assessed. Observations, theory, and models, with increasing robustness, indicate rising global TC risk for some metrics that are projected to impact multiple regions. A 2°C anthropogenic global warming is projected to impact TC activity as follows. 1) The most confident TC-related projection is that sea level rise accompanying the warming will lead to higher storm inundation levels, assuming all other factors are unchanged. 2) For TC precipitation rates, there is at least medium-to-high confidence in an increase globally, with a median projected increase of 14%, or close to the rate of tropical water vapor increase with warming, at constant relative humidity. 3) For TC intensity, 10 of 11 authors had at least medium-to-high confidence that the global average will increase. The median projected increase in lifetime maximum surface wind speeds is about 5% (range: 1%–10%) in available higher-resolution studies. 4) For the global proportion (as opposed to frequency) of TCs that reach very intense (category 4–5) levels, there is at least medium-to-high confidence in an increase, with a median projected change of +13%. Author opinion was more mixed and confidence levels lower for the following projections: 5) a further poleward expansion of the latitude of maximum TC intensity in the western North Pacific; 6) a decrease of global TC frequency, as projected in most studies; 7) an increase in global very intense TC frequency (category 4–5), seen most prominently in higher-resolution models; and 8) a slowdown in TC translation speed. </section>
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Long Waves and Cyclone Waves

1949-08-01
E. T. Eady
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Influences of Asymmetric Convection on Vertical Alignment of Sheared Tropical Cyclone Vortices in Idealized Experiments

2025-06-25
Yecheng Feng , Liguang Wu , Xingyang Zhou | Journal of the Atmospheric Sciences
Abstract Previous studies have indicated that diabatic heating plays a crucial role in aligning the vortices of tropical cyclones (TCs) at various altitudes within a sheared environment. However, the influence … Abstract Previous studies have indicated that diabatic heating plays a crucial role in aligning the vortices of tropical cyclones (TCs) at various altitudes within a sheared environment. However, the influence of diabatic heating associated with convective asymmetries on the continuous tilt reduction, one pathway toward vortex alignment, remains insufficiently understood. In this study, idealized experiments under a full range of easterly moderate vertical wind shear (VWS) are conducted to investigate the continuous tilt reduction of the simulated TCs. The onset of TC intensification relies on achieving a vertically aligned TC structure while the evolution of the vortex tilt varies nonlinearly with shear magnitude. We demonstrate that the convective asymmetry, mainly enhanced on the downtilt side in the simulated TCs, plays a dominant role in the continuous tilt evolution. On the one hand, the direct influence of diabatic heating associated with the asymmetric convection facilitates the reduction of vortex tilt. On the other hand, the convective asymmetry generates a pair of counterrotating gyres over the inner-core region, with cyclonic (anticyclonic) vorticity located downstream of heating (cooling) regions. This convectively-induced asymmetric flow impedes vertical coupling of TC vortices. The evolution of the vertical tilt is primarily governed by the approximate balance between these two processes. This study highlights the critical importance of understanding convective evolution in TC intensification prediction.

Tropical Sea Surface Warming Patterns and Tropical Cyclone Activity: A Review

2025-06-25
Yuqing Wang , Masaki Satoh , Ruifen Zhan +2 more | Advances in Atmospheric Sciences

Impacts of environment on the sudden track change of super typhoon GAEMI(2024)

2025-06-24
Yiming Ma , Hui Qiu , Baofei Feng +4 more | Frontiers in Earth Science
To improve understanding of essential aspects that influence forecasting of tropical cyclone sudden track change, by using ERA5 reanalysis data provided by the European Centre for Medium-Range Weather Forecasts (ECMWF), … To improve understanding of essential aspects that influence forecasting of tropical cyclone sudden track change, by using ERA5 reanalysis data provided by the European Centre for Medium-Range Weather Forecasts (ECMWF), the synoptic analysis method and the vorticity diagnosis method to explore the reasons for the sudden track change of super typhoon GAEMI(2024). It is found that the subtropical high on the east of the typhoon and the trough on the north are the main synoptic systems affecting the sudden track change. Due to the uneven distribution of the wind field in the vertical direction and the uneven horizontal distribution of vertical motion, the vertical motion tilts the horizontal vorticity to generate a vertical vorticity component. Thus the vorticity tilting term is the main reason for the enhancement of the subtropical high. During the eastward movement of the trough on the north side of the typhoon, its intensity weakened and the bottom of the trough moved northward. And at the same time, the typhoon intensity weakened after landfall, so the westward-extending subtropical high formed a steadily maintained high-pressure dam in the north of the typhoon. Under the combined effect of the above changes in the environmental field, the meridional steering current of the typhoon decreases rapidly, and under the guidance of the upper-level steering flow, the typhoon suddenly turns westward from the northwestward track.

Muted ENSO Modulation of Tropical Cyclone Outer Size Over the Western North Pacific in Recent Decades

2025-06-24
Shi‐Qi Yu , Yipeng Guo , Xin Qiu +2 more | Journal of Geophysical Research Atmospheres
Abstract Utilizing a data set of objectively estimated tropical cyclone (TC) size based on deep learning algorithms, this study investigates the relationship between the interannual variation of TC outer size … Abstract Utilizing a data set of objectively estimated tropical cyclone (TC) size based on deep learning algorithms, this study investigates the relationship between the interannual variation of TC outer size over the western North Pacific and El Niño‐Southern Oscillation (ENSO) during July–September from 1981 to 2017. The size of TCs is measured by the mean radius of gale‐force winds at their lifetime maximum intensity. Our results reveal an abrupt decadal change in the ENSO‐TC size relationship: the annual mean TC size exhibited a strong correlation with the Niño 3.4 SST index before 1998, but this correlation has significantly weakened since then. This change is primarily attributed to the more uniform distributions of cyclone expansion rate (CER) across ENSO phases during the past two decades. Climatically, environmental conditions favorable for TC size expansion weaken with increasing latitude, resulting in a dominant meridional gradient of CER. Before 1998, TC activity displayed a pronounced north‐south contrast between El Niño and La Niña years, leading to a significantly higher mean CER for TCs during El Niño episodes. In recent decades, however, interannual variations in TC genesis density have shifted to a southeast‐northwest dipole pattern. This shift, along with changes in TC tracks, has substantially increased the latitudinal overlap of TC occurrences between warm and cold phases, thereby narrowing differences in CER distributions. Concurrently, changes in environmental conditions have become more favorable for TC size expansion during La Niña years, further reducing disparities in TC size distributions across ENSO phases.

Intense humid heat ─ tropical cyclone compound hazards in eastern coastal India

2025-06-24
Poulomi Ganguli , Ning Lin | npj natural hazards.

Impacts of Typhoon Tracks on Frontal Changes Modulating Chlorophyll Distribution in the Pearl River Estuary

2025-06-24
Qinghao Zhao , Qibin Lao , Chao Wang +2 more | Remote Sensing
Typhoons can significantly alter ocean hydrodynamic processes through their powerful external forces, greatly affecting marine biogeochemistry and ocean productivity. However, the specific impacts of typhoons with different tracks on coastal … Typhoons can significantly alter ocean hydrodynamic processes through their powerful external forces, greatly affecting marine biogeochemistry and ocean productivity. However, the specific impacts of typhoons with different tracks on coastal dynamics, including frontal activities and phytoplankton lateral transport, are not well understood. This study captured two distinct types of typhoons, namely Merbok (2017) and Nuri (2020), which landed from the right and left sides of the Pearl River Estuary (PRE), respectively, utilizing satellite remote sensing data to study their impacts on frontal dynamics and marine productivity. We found that after both typhoons, the southwest monsoon amplified geostrophic currents significantly (increased ~14% after Nuri (2020) and 48% after Merbok (2020)). These stronger currents transported warmer offshore seawater from the South China Sea to the PRE and intensified the frontal activities in nearshore PRE (increased ~47% after Nuri (2020) and ~2.5 times after Merbok (2020)). The ocean fronts limited the transport of high-chlorophyll and eutrophic water from the PRE to the offshore waters due to the barrier effect of the front. This resulted in a sharp drop in chlorophyll concentrations in the offshore-adjacent waters of PER after Typhoon Nuri (2020) (~37%). By contrast, despite the intensified geostrophic current induced by the summer monsoon following Typhoon Merbok (2020), its stronger offshore force, driven by the intense offshore wind stress (characteristic of the left-side typhoon), caused the nearshore front to move offshore. The displacement of fronts lifted the restriction of the front barrier and led more high-chlorophyll (increased ~4 times) and eutrophic water to be transported offshore, thereby stimulating offshore algal blooms. Our findings elucidate the mechanisms by which different track typhoons influence chlorophyll distribution through changes in frontal dynamics, offering new perspectives on the coastal ecological impacts of typhoons and further studies for typhoon impact modeling or longshore management.

Long‐Lived Concentric Eyewalls in Numerically Simulated Typhoon Lekima (2019)

2025-06-24
Nannan Qin , Qingyuan Liu | Geophysical Research Letters
Abstract Typhoon Lekima (2019) exhibited a long‐lived concentric eyewall (LLCE) structure, which was successfully simulated using the Weather Research and Forecasting model. The simulation captured the LLCE, including a nearly … Abstract Typhoon Lekima (2019) exhibited a long‐lived concentric eyewall (LLCE) structure, which was successfully simulated using the Weather Research and Forecasting model. The simulation captured the LLCE, including a nearly steady inner eyewall and an expanding outer eyewall indicated by the radius of the maximum tangential wind (RMW). The RMW budget diagnostics reveal that the radial advection of momentum is balanced by the vertical advection of momentum and diffusion at the inner RMW. This dynamic balance maintains a near‐zero radial gradient of tangential wind tendency, thereby supporting a steady inner eyewall with a sharpening tangential wind profile. The inward‐propagating rainbands enhance tangential winds outside the outer eyewall, maintaining a positive radial gradient of tangential wind tendency and facilitating the outer RMW expansion. These processes produce a wide moat, which prolongs the duration of the CE by weakening the suppression of the outer eyewall on the inner eyewall.

Tropical Cyclone Seed Disturbances in ERA5

2025-06-24
Jihong Moon , Daehyun Kim , Allison A. Wing +4 more | Journal of Climate
Abstract Tropical cyclone (TC) seed disturbances are moist synoptic-scale cyclonic circulation features that can potentially develop into TCs. This study tracks TC seed disturbances in the fifth generation European Centre … Abstract Tropical cyclone (TC) seed disturbances are moist synoptic-scale cyclonic circulation features that can potentially develop into TCs. This study tracks TC seed disturbances in the fifth generation European Centre for Medium-range Weather Forecast Reanalysis for the period of 1980-2023 and investigates the characteristics of the tracked disturbances. Using TempestExtremes, the tracking algorithm finds spatiotemporally connected 850-hPa geopotential local minima that satisfy a set of gradient wind, relative vorticity and relative humidity conditions. Over the 44 years, we found 43,777 seed disturbances with an average survival rate (fraction that become a TC) of about 6.5%. The geographical distribution of the genesis and track density of the TC seed disturbances resembles that of TCs, as they predominantly develop in regions characterized by high sea surface temperature (SST), mid-level relative humidity, and precipitation, and low vertical wind shear. Among the large-scale environmental variables, relative humidity and SST best explains the inter-basin difference in the mean TC seed frequency and survival rate, respectively. Among TC seed disturbances that develop into TCs, those with strong precipitation tend to develop into TCs more rapidly. A comparison to other seed disturbance datasets reveals that the overall number of seed disturbances, hence the survival rate, is highly sensitive to the variables used to define TC seeds, as well as the thresholds considered in the tracking algorithms.

Investigation of the Vertical Structure of Tropical Cyclones by WRF Model

2025-06-24
Kh Hafizur Rahman , Mohammad Abdullah Taher | Journal of Engineering Science
Tropical cyclones (TCs) are the most destructive atmospheric phenomena regarding damage to lives and properties over the coastal regions. An attempt has been made to examine the vertical structure of … Tropical cyclones (TCs) are the most destructive atmospheric phenomena regarding damage to lives and properties over the coastal regions. An attempt has been made to examine the vertical structure of two TCs (Amphan and Bulbul) formed over the Bay of Bengal (BoB) with unlike intensities. Weather Research and Forecasting (WRF) model is deployed to simulate the selected TCs. The model is configured with two two-way interactive nested domains with a horizontal resolution of 27 km and 9 km. Outputs from the 9 km domain are considered for analysis. The vertical structure of different parameters like tangential and radial wind, relative humidity, vorticity, vertical velocity, etc. are examined. WRF model is capable enough to simulate the vertical structure of different parameters. It was found that Amphan’s structure is simulated realistically better as compared to Bulbul. Investigation of the vertical structure of TCs would enhance the knowledge in understanding the role of vertical structure in predicting TCs intensity as well as movement. Journal of Engineering Science 15(2), 2024, 41-50

Atlantic Niño increases early-season tropical cyclone landfall risk in Korea and Japan

2025-06-23
Dongmin Kim , Sang‐Ki Lee , Hosmay Lopez +4 more | npj Climate and Atmospheric Science

Synergy Between Polar-Orbiting and Geostationary Sensors in Estimating Near Surface Winds Over the Oceanic Region: A Tropical Cyclone Case Study

2025-06-23
Neeru Jaiswal , Randhir Singh , P. K. Thapliyal | Journal of the Indian Society of Remote Sensing

Response of the Yellow and East China seas low-trophic ecosystems to two typhoons at different translational speeds

2025-06-23
Lei Zhu , Jing Zhang , Can Shi +6 more | Journal of Oceanology and Limnology

The solar influenced cyclone genesis modelling: North Indian Ocean region

2025-06-23
Syed Ahmad Hassan , Shehzeen Khalid Maskar , Mehwish Shafi Khan | Modeling Earth Systems and Environment

Change in tropical cyclone size over the western North Pacific

2025-06-23
Yalan Zhang , Yixuan Shen , Yuan Sun +3 more | Research Square (Research Square)
<title>Abstract</title> Tropical cyclone (TC) size is a key factor in determining TC destructiveness and a major challenge in understanding changes in TCs. Although much effort has been devoted to investigating … <title>Abstract</title> Tropical cyclone (TC) size is a key factor in determining TC destructiveness and a major challenge in understanding changes in TCs. Although much effort has been devoted to investigating TC track and intensity changes, relatively few studies have focused on TC size changes, particularly their responses to natural variability and global warming. Here, we use a metric of TC size in which TCs achieve their lifetime-maximum intensity, which is relatively insensitive to uncertainty in past data. The results show that the Interdecadal Pacific Oscillation (IPO) dominates TC size variability in the western North Pacific, which is the most active region for TCs. Moreover, TC size variability is governed primarily by radial sea surface temperature (SST) gradients rather than absolute SST values. This finding explains not only the difference in TC size between IPO positive and negative years but also the stronger correlation between the IPO and TC size than other climate indices, such as El Niño–Southern Oscillation (ENSO), since the IPO is derived from SST differences and thus gradients, whereas ENSO is determined by absolute SST values. This finding further implies that the pattern rather than the magnitude of the SST change will determine the change in TC size under future global warming.

How rare was the 2016–2022 tropical cyclone activity near the Caribbean coasts of Nicaragua and Costa Rica?

2025-06-22
Hugo G. Hidalgo , Tosiyuki Nakaegawa , David Romero +4 more | Natural Hazards

Tabonuco and Plantation Forests at Higher Elevations Are More Vulnerable to Hurricane Damage and Slower to Recover in Southeastern Puerto Rico

2025-06-21
Michael William Caslin , Madhusudan Katti , Stacy A. C. Nelson +1 more | Land
Hurricanes are major drivers of forest structure in the Caribbean. In 2017, Hurricane Maria caused substantial damage to Puerto Rico’s forests. We studied forest structure variation across 75 sites at … Hurricanes are major drivers of forest structure in the Caribbean. In 2017, Hurricane Maria caused substantial damage to Puerto Rico’s forests. We studied forest structure variation across 75 sites at Las Casas de la Selva, a sustainable forest plantation in Patillas, Puerto Rico, seven years after Hurricane Maria hit the property. At each site we analyzed 360° photos in a 3D VR headset to quantify the vertical structure and transformed them into hemispherical images to quantify canopy closure and ground cover. We also computed the Vertical Habitat Diversity Index (VHDI) from the amount of foliage in four strata: herbaceous, shrub, understory, and canopy. Using the Local Bivariate Relationship tool in ArcGIS Pro, we analyzed the relationship between forest recovery (vertical structure, canopy closure, and ground cover) and damage. Likewise, we analyzed the effects of elevation, slope, and aspect, on damage, canopy closure, and vertical forest structure. We found that canopy closure decreases with increasing elevation and increases with the amount of damage. Higher elevations show a greater amount of damage even seven years post hurricane. We conclude that trees in the mixed tabonuco/plantation forest are more susceptible to hurricanes at higher elevations. The results have implications for plantation forest management under climate-change-driven higher intensity hurricane regimes.

GIS, Remote Sensing and Machine Learning: Data Integration to Support the Management of Coastal Island Ecosystems

2025-06-21
David J. Lieske , Stephanie Avery‐Gomm , Patrick Champagne +1 more | Environmental Management
Islands are important components of many coastal areas around the world; however, by virtue of their geographical isolation, the state of these ecosystems is often poorly known. To address the … Islands are important components of many coastal areas around the world; however, by virtue of their geographical isolation, the state of these ecosystems is often poorly known. To address the knowledge gap for the province of Nova Scotia, Canada, geographic information systems (GIS), remote sensing (RS), and machine learning (ML) were used to examine the status of nearly 4000 islands. We classified islands topographically and determined, based on 1 m resolution LiDAR, that approximately 70% are <2 m average elevation and highly vulnerable to partial or complete flooding under near-term regimes of sea level rise and storm surge potential. Vegetation cover was strongly related to topographic class, with higher, more steeply-sided islands having more tree cover and less sand, rock, and wetland. Climatic changes were most pronounced in the form of sea surface temperature (SST) warming, with August changes (+0.063 °C yr-1) being 6.3× higher than the global mean background rate, particularly affecting the Gulf of St. Lawrence subregion. Human activity, in the form of marine traffic, is a pervasive stress. To integrate all these factors, a random forest ML model was trained using tree mortality from forest inventory records as the environmental response, and the predictions were used to define a region-wide Ecosystem Stress Index (ESI). These findings demonstrate the kinds of insights geospatial data and ML can provide, and offer tools for improving our understanding of coastal island vulnerability.

Machine Learning-based Statistical Prediction of Cyclonic Disturbance Frequency during Post-monsoon over the Bay of Bengal

2025-06-21
Javed Akhter , Aditi Bhattacharyya , Subrata Kumar Midya | Pure and Applied Geophysics

Tropical cyclone impact data in the Philippines: implications for disaster risk research

2025-06-20
Elizabeth G. Galloway , Jennifer L. Catto , Chunbo Luo +1 more | Natural Hazards
Abstract Natural hazards such as tropical cyclones (TCs) cause widespread destruction. Historical impact data provides a resource for understanding TC impacts and associated societal vulnerabilities which is essential for building … Abstract Natural hazards such as tropical cyclones (TCs) cause widespread destruction. Historical impact data provides a resource for understanding TC impacts and associated societal vulnerabilities which is essential for building resilience. However, characteristics of impact data such as resolution and coverage can influence its utility for disaster risk reduction (DRR) applications. With this in mind, we present a province-level impact dataset for TCs in the Philippines between 2010 and 2020 for deaths, affected population, housing damage and economic loss curated for DRR applications. Specifically, we evaluate the effect of the dataset’s spatial resolution and its coverage of hazard intensities, impact magnitudes and impact types and discuss the implications for DRR applications. Considering the utility of impact data within the context of DRR is crucial, and a dataset with comprehensive coverage of impact and hazard magnitudes and appropriate spatial resolution is pivotal for DRR applications. The research presents a guide for others using this dataset and data more generally in DRR applications.

Changes in stratiform heating structure due to surface warming weaken and accelerate convectively coupled Kelvin waves

2025-06-20
Mu‐Ting Chien , Daehyun Kim | EarthArXiv (California Digital Library)
Although stratiform heating plays a crucial role in tropical convective systems, we do not fully understand (1) how stratiform heating would change in response to surface warming and (2) how … Although stratiform heating plays a crucial role in tropical convective systems, we do not fully understand (1) how stratiform heating would change in response to surface warming and (2) how those changes would affect convectively-coupled equatorial waves. This study analyzes the changes in stratiform heating structure and convectively-coupled Kelvin waves (KWs) associated with surface warming using a set of aquaplanet simulations. Results show that the melting level rises with warming, causing ice particles falling from the stratiform clouds to melt at lower pressure levels. The upward shift of melting-induced cooling results in a decrease in temperature and vertical motion variability associated with stratiform clouds in the lower free-troposphere and upper boundary layer. These changes lower the degree to which stratiform (i.e., the second baroclinic mode) and deep convective clouds (i.e., the first baroclinic mode) are coupled within KWs, causing KWs to weaken and accelerate with warming.

Precipitation of Weak Tropical Cyclone Mulan (2022): Sensitivity to Cumulus and Microphysics Parameterization Schemes

2025-06-20
Jingyao Wang , Ein‐Fen Yu , Jiehua Ma +3 more | Journal of Geophysical Research Atmospheres
Abstract Previous studies on precipitation caused by tropical cyclones (TCs) have largely focused on strong TCs while systematic research on weak systems remains limited. This study utilized the high‐resolution (3 … Abstract Previous studies on precipitation caused by tropical cyclones (TCs) have largely focused on strong TCs while systematic research on weak systems remains limited. This study utilized the high‐resolution (3 km) weather research and forecasting (WRF) model to investigate the sensitivity of heavy precipitation generated by weak TC Mulan (2022) over the South China Sea to cumulus and microphysics parameterization schemes. Six cumulus parameterizations and five microphysics schemes were configured with simulations validated against gauge observations. Results indicated that cumulus parameterizations had a significant influence on precipitation simulation while the microphysics schemes exhibited a relatively minor impact in this case. The combination of the New Tiedtke cumulus scheme and the WRF Single‐Moment 6‐class (WSM6) microphysics scheme yielded the best simulation of precipitation compared with the observations. Further investigation revealed that cumulus parameterizations modulated simulated large‐scale circulation, moisture transportation, and vertical velocities. The New Tiedtke scheme reproduced a more northward TC track and an intensified southeast jet along the coast of Southeast China, aligning with the observed heavy precipitation zones and providing favorable dynamic and thermodynamic conditions for precipitation. In contrast, the Betts‐Miller‐Janjić (BMJ) scheme resolved cloud‐environment interactions inadequately, resulting in excessive convection and latent heating, which amplified cumulus precipitation compared to the New Tiedtke scheme. Among the cumulus parameterization schemes, the Kain‐Fritsch (KF) and BMJ schemes underperformed due to their overestimation of deep convection while the New Tiedtke and Multi‐scale KF (MSKF) schemes showed better performance. This study provides a valuable reference for further precipitation prediction research in the study region and adjacent areas.

ASM-SS: the first quasi-global high-spatial-resolution coastal storm surge dataset reconstructed from tide gauge records

2025-06-20
Lianjun Yang , Taoyong Jin , Weiping Jiang | Earth system science data
Abstract. Storm surges (SSs) cause massive loss of life and property in coastal areas each year. High-spatial-coverage and long-term SS records are the basis for deepening our understanding of these … Abstract. Storm surges (SSs) cause massive loss of life and property in coastal areas each year. High-spatial-coverage and long-term SS records are the basis for deepening our understanding of these disasters. Due to the sparse and uneven distribution of tide gauge stations, such global or quasi-global information can only be provided by global numerical models, while their simulation products mainly span the most recent decades. In this paper, for the first time, an all-site modeling framework for a data-driven model was implemented on a quasi-global scale within areas severely affected by SSs caused by tropical cyclones. Using tide gauge records and European Centre for Medium-Range Weather Forecasts (ECMWF) Reanalysis v5 (ERA5) data, we generated a high-spatial-resolution (10 km along the coastline) hourly SS dataset, ASM-SS (all-site modeling storm surge), within the span 45° S–45° N, whose record length is over 80 years from 1940 to 2020. Assessments indicate that, for 95th extreme SSs, the precision of the ASM-SS model (the medians of the correlation coefficients, root mean square errors, and mean biases are 0.63, 0.093, and −0.050 m, respectively) is better than that of the state-of-the-art global hydrodynamic model (the medians are 0.55, 0.106, and −0.045 m). For annual maximum SSs, it is more stable than the numerical model, with the overall root mean square error and coefficient of determination optimizing by 22.3 % and 14.8 %, respectively. This dataset could provide possible alternative support for coastal communities through relevant SS analysis applications requiring high spatial resolution and sufficiently long records. The ASM-SS dataset is available at https://doi.org/10.5281/zenodo.14034726 (Yang et al., 2024a).
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Tropical cyclone probability estimation in data-sparse regions: a subtropical high based approach

2025-06-19
Jingyi Lu , Jiazi Li , Zhenguo Wang +6 more | Natural Hazards

Assessing the impact of coastal flooding along the northern Yucatan Peninsula associated to sea level rise under different shared socio-economic pathways

2025-06-19
Wilmer Rey , Paulo Salles , José Carlos Pintado‐Patiño +4 more | Natural Hazards
Abstract Sea level rise (SLR) inundation threats were evaluated across four barrier island coastal socio-ecosystems in the northwestern Yucatan Peninsula. Firstly, a 2-D hydrodynamic model was implemented, using a high-spatial-resolution … Abstract Sea level rise (SLR) inundation threats were evaluated across four barrier island coastal socio-ecosystems in the northwestern Yucatan Peninsula. Firstly, a 2-D hydrodynamic model was implemented, using a high-spatial-resolution LIDAR Digital Elevation Model, and was forced with SLR projections (17th- 83rd percentiles) for the year 2100 under three Shared Socio-economic Pathways (SSP) (SSP1-2.6, SSP2-4.5, and SSP5-8.5) along with the local micro tide. Model results suggest important impacts in these coastal communities, particularly under the worst-case flood scenario (SSP5-8.5 83rd percentile; spring high tide), projecting flooding in 22–64% of city blocks of those towns by 2100. Moreover, rapid population growth over the past ten years has further increased flood risks. Further analysis focusing on Progreso, the largest coastal town in the study region, flood, population, and land use cover maps were overlaid to exhibit exposed elements to floods. This analysis reveals that large portions of forests (43.45%), shrublands (32.35%), grasslands (21.68%), and artificial surfaces (2.51%), and numerous city blocks in the lee side of the barrier island could be flooded under this worst-case flood scenario. Secondly, different alternatives to reduce the exposure to coastal flooding (levees, inhabitant’s relocation, land elevation build-up, and stilt houses) are discussed. This methodology can be useful to decision-makers for prevention, preparedness, mitigation of SLR impacts, and updating land use in northern Yucatan and other similar coastal regions.

Tropical Cyclone-Radiation Interaction in NASA Reanalysis and Model Products as Compared to CloudSat Observations

2025-06-19
Tsung-Yung Lee , Allison A. Wing | Journal of the Atmospheric Sciences
Abstract Tropical cyclone (TC)-radiation interaction is important in TC development in which the structure of moisture and cloud modulate radiation. This study validates the representation of moisture, cloud and TC-radiation … Abstract Tropical cyclone (TC)-radiation interaction is important in TC development in which the structure of moisture and cloud modulate radiation. This study validates the representation of moisture, cloud and TC-radiation interaction in the products of the Goddard Earth Observing System atmospheric model, version 5.12.4 (GEOS5) by utilizing a satellite-based observational estimation of TC-radiation interaction from the CloudSat Tropical Cyclone (CSTC) dataset. The GEOS5 products include the Modern-Era Retrospective Analysis for Research and Application, Version 2 (MERRA-2), and the MERRA-2 Atmospheric Model Intercomparison Project (AMIP) set of simulations (M2AMIP). Under similar TC intensity, GEOS5 TCs experience a comparable longwave (LW)-cloud feedback to that in CSTC despite having at least an order of magnitude less cloud ice mass. This results from the presence of upper-tropospheric ice clouds which are efficient at reducing the outgoing LW radiation. The clear-sky LW feedback is greater in GEOS5 TCs which results from a greater occurrence frequency of dry conditions in the TC’s outer region. The LW radiatively-driven circulation favors TC development while the SW-driven circulation is confined to the upper troposphere and modulates the circulation at the outflow layer. TCs in CSTC experience a deep-layer LW radiatively-driven circulation, while that in GEOS5 TCs is confined to the upper troposphere and is less effective at supporting TC development, which might contribute to the low intensity bias of GEOS5 TCs. The top-heavy distribution of ice in GEOS5 TC restricts the radiatively-driven circulation to the upper troposphere. The small discrepancies between GEOS5 outputs indicates that the data assimilation process for MERRA-2 does not substantially alter the TC-radiation interaction in GEOS5.

Verifying WPC Excessive Rainfall Outlooks across three hurricanes of varying rainfall impact

2025-06-19
Alexandra Music , J. Marshall Shepherd | Research Square (Research Square)
<title>Abstract</title> Atlantic basin hurricanes drive serious meteorological hazards for the southeast United States, including rainfall-induced flooding. The well-known Saffir-Simpson Hurricane Wind Scale communicates only wind hazard, creating the potential for … <title>Abstract</title> Atlantic basin hurricanes drive serious meteorological hazards for the southeast United States, including rainfall-induced flooding. The well-known Saffir-Simpson Hurricane Wind Scale communicates only wind hazard, creating the potential for low wind, high rainfall storms to be perceived as mild. Researchers have emphasized the need to center rainfall hazard in hurricane warning messaging, and prerequisite to this is verifying the accuracy of hurricane rainfall forecasts. This paper investigates the characterization of forecasted and observed rainfall for three Atlantic hurricanes with varying rainfall impact: Florence (2018), Michael (2018), and Ian (2022). We first quantified, visualized, and compared the distribution of daily and total rainfall for each storm to establish the concept of varied rainfall impact. By a Mann-Whittney U Test, we found that the distributions of total rainfall for Florence/Michael and Florence/Ian were significantly different while differences between Michael/Ian were not significant. We then compared Excessive Rainfall Outlooks (EROs) against a flash flood proxy both visually and through fractional coverage calculations. We used these to calculate fractions brier scores (FBS) and fractions skill scores (FSS) using old and new ERO definitions. New ERO definitions improved FSS scores across all hurricanes. Florence had the highest FSS, followed by Michael, then Ian, though all scores were deemed skillful. To the authors’ knowledge, this is the first instance of FSS scores used for ERO verification. These findings provide a framework for a wider study on forecast verification across hurricane rainfall scenarios, a key step towards improving how we communicate and characterize these hazards.

An Improved Physics-Based Hurricane Track Model over the North Atlantic Basin with Its Application for Wind-Hazard Assessment

2025-06-19
Chao Sheng , Paolo Bocchini | Journal of Structural Engineering

An Atmospheric Predictor to Estimate the Atmospherically Induced Water Level at Coasts With A Shallow Continental Shelf

2025-06-18
Paula Gomes da Silva , Luana Borato , Antonio Fernando Härter Fetter Filho +2 more | International Journal of Climatology
ABSTRACT Due to the connection between atmospheric conditions and the marine climate, previous studies proposed the use of atmospheric data as a predictor to estimate the total water level at … ABSTRACT Due to the connection between atmospheric conditions and the marine climate, previous studies proposed the use of atmospheric data as a predictor to estimate the total water level at the coast. However, none of the previous applications considered the effect that a large and shallow continental shelf may have on the propagation of water level variables, such as the storm surge. The shallow bathymetry facilitates the occurrence of coastal trapped waves, and the storm surge signal may present a strong component generated in remote regions. This phenomenon must be considered when defining the atmospheric predictor in these areas. This work presents a methodology to define the best atmospheric predictor to describe waves, storm surge and total water level in this particular kind of coasts. The method was applied in a location on the southern coast of Brazil (Southwest Atlantic), where the effect of the shallow bathymetry in the storm surge was previously observed. A statistical relationship between the atmospheric predictor and water level variables at three coastal points was established to assess its ability to estimate atmospheric‐induced water levels and their components. High Pearson correlation coefficients ( r &gt; 0.78 for all variables) and errors comparable to those obtained by traditional numerical methods demonstrate the skill of the predictor to describe the variables related to the water level at the coast. The implications of the atmospheric predictor extend beyond water level estimation, including several applications. Some of these applications are shown here, such as the characterisation of average and extreme marine climate and the assessment of climate‐induced variability.

Effectiveness of the Ike Dike in mitigating coastal flood risk under multiple climate and sea level rise projections

2025-06-18
Seokmin Son , Chaoran Xu , Meri Davlasheridze +2 more | Risk Analysis
Abstract In the aftermath of Hurricane Ike in 2008 in the United States, the “Ike Dike” was proposed as a coastal barrier system, featuring floodgates, to protect the Houston‐Galveston area … Abstract In the aftermath of Hurricane Ike in 2008 in the United States, the “Ike Dike” was proposed as a coastal barrier system, featuring floodgates, to protect the Houston‐Galveston area (HGA) from future storm surges. Given its substantial costs, the feasibility and effectiveness of the Ike Dike have been subjects of investigation. In this study, we evaluated these aspects under both present and future climate conditions by simulating storm surges using a set of models. Delft3D Flexible Mesh Suite was utilized to simulate hydrodynamic and wave motions driven by hurricanes, with wind and pressure fields spatialized by the Holland model. The models were validated against data from Hurricane Ike and were used to simulate synthetic hurricane tracks downscaled from several general circulation models and based on different sea level rise projections, both with and without the Ike Dike. Flood maps for each simulation were generated, and probabilistic flood depths for specific annual exceedance probabilities were predicted using annual maxima flood maps. Building damage curves were applied to residential properties in the HGA to calculate flood damage for each exceedance probability, resulting in estimates of expected annual damage as a measure of quantified flood risk. Our findings indicate that the Ike Dike significantly mitigates storm surge risk in the HGA, demonstrating its feasibility and effectiveness. We also found that the flood risk estimates are sensitive to hurricane intensity, the choice of damage curve, and the properties included in the analysis, suggesting that careful consideration is needed in future studies.

pyTCR: A tropical cyclone rainfall model for python

2025-06-18
Phong V. V. Le , Geeta Persad , Gabriel Pérez +3 more | The Journal of Open Source Software

Modeling North Atlantic Tropical Cyclone Counts Directly From Sea Surface Temperature Maps

2025-06-18
Daniel Wesley , Michael Mann , Bhuvnesh Jain +2 more | Geophysical Research Letters
Abstract Annual North Atlantic tropical cyclone (TC) counts are frequently modeled as a Poisson process with a state‐dependent rate. Current models based on Poisson regression can explain roughly 50% of … Abstract Annual North Atlantic tropical cyclone (TC) counts are frequently modeled as a Poisson process with a state‐dependent rate. Current models based on Poisson regression can explain roughly 50% of the annual variance using three climate indices: El Niño/Southern Oscillation, average sea surface temperature (SST) in the main development region of the North Atlantic, and the North Atlantic oscillation atmospheric circulation index. We introduce a new method, based on the Elastic Net (EN) that predicts TC counts directly from global SST maps. We show it achieves performance on par with current models, without requiring manually constructed indices. To understand the performance of the EN we argue that, when TC counts are generated by independent Poisson draws, statistical models are subject to a lower limit on prediction error. We estimate this limit and show that it is saturated by both current models and our new method.

Long-term water entry impact force forecasting using LSTM-RF with recursive prediction strategy

2025-06-17
Xinyu Wu , Xiaoyi Li , Chang Yuan +4 more | Ships and Offshore Structures

The 2024 Eastern Pacific Hurricane Season: Quiet By Comparison

2025-06-17
Leigh Kelly | Weatherwise

Tropical cyclone response to ambitious decarbonization scenarios

2025-06-17
Mincheol Moon , Seung‐Ki Min , Jung‐Eun Chu +4 more | npj Climate and Atmospheric Science

Anomalous Behavior in Weather Forecast Uncertainty: Implications for Ship Weather Routing

2025-06-17
Marijana Marjanović , Jasna Prpić-Oršić , Anton Turk +1 more | Journal of Marine Science and Engineering
Ship weather routing is heavily dependent on weather forecasts. However, the predictive nature of meteorological models introduces an unavoidable level of uncertainty which, if not accounted for, can compromise navigational … Ship weather routing is heavily dependent on weather forecasts. However, the predictive nature of meteorological models introduces an unavoidable level of uncertainty which, if not accounted for, can compromise navigational safety, operational efficiency, and environmental impact. This study examines the temporal degradation of forecast accuracy across certain oceanographic and atmospheric variables, using a six-month dataset for the area of North Atlantic provided by the National Oceanic and Atmospheric Administration (NOAA). The analysis reveals distinct variable-specific uncertainty trends with wind speed forecasts exhibiting significant temporal fluctuation (RMSE increasing from 0.5 to 4.0 m/s), while significant wave height forecasts degrade in a more stable and predictable pattern (from 0.2 to 0.9 m). Confidence intervals also exhibit non-monotonic evolution, narrowing by up to 15% between 96–120-h lead times. To address these dynamics, a Python-based framework combines distribution-based modeling with calibrated confidence intervals to generate uncertainty bounds that evolve with forecast lead time (R2 = 0.87–0.93). This allows uncertainty to be quantified not as a static estimate, but as a function sensitive to both variable type and prediction horizon. When integrated into routing algorithms, such representations allow for route planning strategies that are not only more reflective of real-world meteorological limitations but also more robust to evolving weather conditions, demonstrated by a 3–7% increase in travel time in exchange for improved safety margins across eight test cases.

RTCP-Net: Tropical cyclone generation prediction model based on multi-source information fusion

2025-06-17
Wei Tian , Xiaotian Li , Jiachen Fan +1 more | Research Square (Research Square)
<title>Abstract</title> Tropical cyclones are among the most destructive extreme weather phenomena in nature, and accurately predicting whether a tropical cloud cluster will develop into a tropical cyclone is crucial for … <title>Abstract</title> Tropical cyclones are among the most destructive extreme weather phenomena in nature, and accurately predicting whether a tropical cloud cluster will develop into a tropical cyclone is crucial for disaster prevention and mitigation. Considering the insufficient extraction of numerous key features in tropical cloud cluster data by previous deep learning-based tropical cyclogenesis prediction studies, in response, this paper proposes the Real Time Tropical Cyclogenesis Prediction-Net (RTCP-Net) based on multi-source information fusion. The model computes convective core maps and polar coordinate representations from infrared images of tropical cloud clusters and employs ResNet along with self-attention mechanism to extract their spatiotemporal features. Experimental results demonstrate that the proposed model achieves high accuracy and stability, it attains a detection rate of 99.4\% and a false alarm rate of 0.36\% when predicting the formation of tropical cyclones 24 hours in advance. Notably, the model not only ensures potential of real-time prediction capabilities from satellite data but also surpasses the accuracy of models that utilize reanalysis data.

Advancing spatio-temporal storm surge prediction with hierarchical deep neural networks

2025-06-17
Saeed Saviz Naeini , Reda Snaiki , Teng Wu | Natural Hazards

The 2024 Atlantic Hurricane Season: Helene and Milton Highlight Five U.S. Hurricane Landfalls

2025-06-17
Andrew B. Hagen | Weatherwise

Development of a land–river–ocean coupled model for compound floods jointly caused by heavy rainfall and storm surges in large river delta regions

2025-06-16
Anyifang Zhang , Xiping Yu | Hydrology and earth system sciences
Abstract. The simultaneous or sequential occurrence of different flood processes, including extreme storm surges and heavy precipitation, tends to trigger compound floods, which are often destructive to life and property. … Abstract. The simultaneous or sequential occurrence of different flood processes, including extreme storm surges and heavy precipitation, tends to trigger compound floods, which are often destructive to life and property. However, numerical models that fully represent the effect of various flood processes and their interactions have not yet been firmly established. In this study, a coupled land–river–ocean model is developed that considers storm surges, storm waves, astronomical tides, river flow, and precipitation. The coupled model is applied to the simulation of compound floods induced by tropical cyclones in the Pearl River Delta. The numerical results obtained on river flow and ocean surface elevation are shown to agree well with observations for cases considered, with Willmott skill values of 0.96 and 0.88, respectively. The coastal inundation area obtained with the model covers approximately 80 % of the area identified by remote sensing. An attribution analysis implies that ocean processes contribute to more than half of the total flood volume, while precipitation accounts for 5 % to 15 % through a tropical cyclone event in the Pearl River Delta region. Significantly, the contribution of river base flow varies from 2 % to 30 % depending on the landfall time of the tropical cyclone. It is also emphasized that the completeness of the coupling method substantially affects the numerical accuracy.

Comparative Analysis of Storm Surge Reconstructions in the Western North Pacific: Implications for Coastal Flood Risk Assessment

2025-06-16
Mengzhen Fan , Wen Dang , Jianlong Feng +2 more | International Journal of Disaster Risk Science
Abstract Storm surges in the Western North Pacific cause significant economic damage and loss of life, highlighting the need for accurate storm surge predictions. This study evaluated four storm surge … Abstract Storm surges in the Western North Pacific cause significant economic damage and loss of life, highlighting the need for accurate storm surge predictions. This study evaluated four storm surge models: the Global Tide and Surge Model (GTSMv3.0), ERA20C neural network (ERA20C_nn), ERA20C multiple linear regression (ERA20C_ml), and 20th Century Reanalysis multiple linear regression (20CR_ml), using data from 160 tidal stations. The results show that the ERA20C_nn model outperformed others, with the highest correlation to tide-gauge observations. The GTSMv3.0 model follows closely, although slightly less accurate. The ERA20C_ml and 20CR_ml models were less effective, especially in predicting extreme surges. The ERA20C_nn model also provided more reliable estimates for 100-year return surge levels, outperforming other models. These findings suggest that neural network-based models, particularly ERA20C_nn, are better suited for assessing coastal flood risks in the region.

The Influence of +<scp>SR</scp>/−<scp>EAP</scp> Combined Pattern on Persistent Rainfall During the Pre‐Rainy Season in South China and Its Associated Energetic Conversion

2025-06-16
Weijie Zeng , Lijuan Wang , Zhaoyong Guan +1 more | International Journal of Climatology
ABSTRACT Precipitation data provided by the China Meteorological Administration and ERA5 reanalysis data from 1990 to 2020 are used to analyse the influence of +Silk Road/−East Asia‐Pacific (+SR/−EAP) combined pattern … ABSTRACT Precipitation data provided by the China Meteorological Administration and ERA5 reanalysis data from 1990 to 2020 are used to analyse the influence of +Silk Road/−East Asia‐Pacific (+SR/−EAP) combined pattern on persistent rainfall during the pre‐rainy season in South China (PRPSC) and its associated energetic conversion. The results indicate that the typical +SR/−EAP combined pattern is significantly correlated with the PRPSC. The development of the combined pattern results in the southward shift of the western Pacific subtropical high (WPSH), facilitating the transport of water vapour from the western Pacific to South China. Meanwhile, the South Asian high (SAH) intensifies and extends eastward, with its eastern boundary overlapping the western boundary of the WPSH along the East Asian coast, favouring the precipitation in South China. During the persistence of the combined pattern, integrated moisture flux convergence occurs in South China, with positive vorticity in the lower levels and negative vorticity in the upper levels, resulting in increased precipitation. The +SR/−EAP combined pattern develops by extracting energy from the basic flow via both barotropic and baroclinic energy conversions. However, since the barotropic energy conversion is relatively small and inefficient, the maintenance of the combined pattern mainly relies on baroclinic energy conversion to obtain available potential energy from the basic flow. Barotropic and baroclinic energy conversions primarily occur in regions north of 30°N, effectively supporting the anomalous centres of the +SR/−EAP pattern in mid‐to‐high latitudes. Baroclinic energy conversion is positive in both the upper and lower troposphere. However, the energy conversion in the upper troposphere exceeds that in the lower, which shows that the baroclinic energy conversion contributes more significantly to the maintenance of the +SR pattern.

Enhancing real time tropical cyclone intensity estimation using YOLO-NAS algorithm with CLEO optimizer

2025-06-15
P. Nandal , Sunesh Malik | International Journal of Systems Assurance Engineering and Management

Improvement on Prediction of Tropical Cyclone ‘Fani’ by Assimilating Quality Controlled Indian DWR Radial Wind: A Case Study

2025-06-14
Sujata Pattanayak , Amarjyothi Kasimahanthi , A. Routray +1 more | Pure and Applied Geophysics

Prehistoric shifts in tropical cyclone season in the South China sea: evidence from daily resolution records of giant clam shells

2025-06-14
Nanyu Zhao , Hong Yan , Ge Shi +4 more | npj Climate and Atmospheric Science

Thermodynamic Study of a Mediterranean Cyclone with Tropical Characteristics in September 2020

2025-06-14
Sotirios Arsenis , Angelos I. Siozos , P. T. Nastos | Atmosphere
This study examines the evolution, structure, and dynamic and thermodynamic mechanisms of a Mediterranean tropical-like cyclone (TLC), or medicane (from Mediterranean–Hurricane), that occurred in the central Mediterranean region from 15 … This study examines the evolution, structure, and dynamic and thermodynamic mechanisms of a Mediterranean tropical-like cyclone (TLC), or medicane (from Mediterranean–Hurricane), that occurred in the central Mediterranean region from 15 to 19 September 2020. This event is considered an extreme meteorological phenomenon, particularly impacting the Greek area and affecting the country’s economic and social structures. It is one of the most significant recorded Mediterranean cyclone phenomena in the broader Mediterranean region. The synoptic and dynamic environment, as well as the thermodynamic structure of this atmospheric disturbance, were analyzed using thermodynamic parameters. The system’s development can be described through three distinct phases, characterized by its symmetrical structure and warm core, as illustrated in the phase space diagrams and further supported by dynamical analysis. During the first phase, on 15 September, the structure of the upper tropospheric layers began to strengthen the parent barometric low, which had been in the Sirte Bay region since 13 September. The influence of upper-level dynamical processes was responsible for the reconstruction of the weakened barometric low. In the second phase, during the formation of the Mediterranean cyclone, low-level diabatic processes determined the evolution of the surface cyclone without significant support from upper-tropospheric baroclinic processes. Therefore, in this phase, the system is characterized as barotropic. In the third phase, the system remained barotropic but showed a continuous weakening tendency as the sea surface pressure steadily increased. This comprehensive analysis highlights the intricate processes involved in the development and evolution of Mediterranean cyclones with tropical characteristics.

The role of fractal geometry in assessing typhoon intensity from remote sensing images

2025-06-14
Xiaojian Yu , H. Chen , Zhonglu Lin | Chaos Solitons & Fractals

The Role of Tropical Cyclone Seeds on Modulating the Seasonal Cycle of Tropical Cyclone Frequency in the North Indian Ocean

2025-06-14
M. Kim , Daehyun Kim , Suzana J. Camargo +2 more | Geophysical Research Letters
Abstract This study investigates the seasonal cycle of tropical cyclones (TCs) in the North Indian Ocean (NIO) using a multi‐stage framework of tropical cyclogenesis that considers the TC seeds and … Abstract This study investigates the seasonal cycle of tropical cyclones (TCs) in the North Indian Ocean (NIO) using a multi‐stage framework of tropical cyclogenesis that considers the TC seeds and TCs separately. We find that the May–June (MJ) pre‐monsoon season features fewer TC seeds (∼23) with high survival rates (SR, ∼2.8%), while the post‐monsoon season October‐November (ON) shows abundant TC seeds (∼66) with low SR (∼1.8%). Genesis potential indices (GPIs), which combine key environmental factors, capture the TC seed numbers and spatial distribution but fail to explain SR differences between seasons. Composite analysis reveals that MJ season TC seeds exhibit more intense convection, suggesting additional sources of instability not included in current GPIs, potentially related to horizontal gradient of moisture. These findings highlight the importance of considering both TC seed numbers and SR when investigating TC frequency in the NIO and show GPIs' limitations that focus solely on local environmental variables.

Aspects-Based Sentiment Analysis of Extreme Weather on Twitter Using Long Short-Term Memory

2025-06-14
Tursun Abdurahmonov , Muhammad Nabil Toby Abiyyu , D. Khayat +1 more | Journal of Informatics and Web Engineering
This study presents an aspect-based sentiment analysis of tweets related to extreme weather events in Indonesia, utilizing the Long Short-Term Memory (LSTM) model. The dataset was obtained through a Twitter … This study presents an aspect-based sentiment analysis of tweets related to extreme weather events in Indonesia, utilizing the Long Short-Term Memory (LSTM) model. The dataset was obtained through a Twitter crawling process, followed by a series of preprocessing steps including data cleaning, stop word removal, normalization, tokenization, and stemming. The three primary areas of emphasis in the study were kinds of bad weather forecasts, and the government or society reactions. Using a lexicon-based technique, sentiment labelling generated three groups: positive, neutral, and negative. A random oversampling method was employed to address the data imbalance. The model using the LSTM algorithm was trained individually for aspect and sentiment classification tasks, so reaching high accuracies of 98.94% and 97.53%, respectively. The results indicate that the model effectively categorises talk on extreme weather and the opinions of the public. A word cloud visual representation was additionally created to show frequently occurring terms in the dataset, thereby offering insights into current themes and sentiment expressions. This work provides valuable input for government agencies and legislators in developing communication and disaster response plans, thereby serving to better understand the public's view on climate-related events. Future work could involve improving techniques for preprocessing and using larger, wider-ranging datasets for improving the model's robustness and generalisation.