Imperial College London

DrShuaiWang

Faculty of Natural SciencesDepartment of Physics

Research Associate in Atmospheric Physics
 
 
 
//

Contact

 

shuai.wang CV

 
 
//

Location

 

709Blackett LaboratorySouth Kensington Campus

//

Summary

 

Publications

Publication Type
Year
to

16 results found

Wang S, Toumi R, Ye Q, Ke Q, Bricker J, Tian Z, Sun Let al., 2021, Is the tropical cyclone surge in Shanghai more sensitive to landfall location or intensity change?, Atmospheric Science Letters, ISSN: 1530-261X

Journal article

Toumi R, Wang S, 2021, Recent migration of tropical cyclones toward coasts, Science, Vol: 371, Pages: 514-517, ISSN: 0036-8075

Poleward migrations of tropical cyclones have been observed globally, but their impact on coastal areas remains unclear. We investigated the change in global tropical cyclone activity in coastal regions over the period 1982–2018. We found that the distance of tropical cyclone maximum intensity to land has decreased by about 30 kilometers per decade, and that the annual frequency of global tropical cyclones increases with proximity to land by about two additional cyclones per decade. Trend analysis reveals a robust migration of tropical cyclone activity toward coasts, concurrent with poleward migration of cyclone locations as well as a statistically significant westward shift. This zonal shift of tropical cyclone tracks may be mainly driven by global zonal changes in environmental steering flow.

Journal article

Wang S, Rashid T, Thorp H, Toumi Ret al., 2020, A shortening of the life-cycle of major tropical cyclones, Geophysical Research Letters, Vol: 47, Pages: 28 Jul 2020-28 Jul 2020, ISSN: 0094-8276

In this study a comprehensive picture of the changing intensity life cycle of major (Category 3 and higher) tropical cyclones (TCs) is presented. Over the past decades, the lifetime maximum intensity has increased, but there has also been a significant decrease in duration of time spent at intensities greater than Category 1. These compensating effects have maintained a stable global mean‐accumulated cyclone energy of individual major TCs. The global mean duration of major TCs has shortened by about 1 day from 1982 to 2018. There has been both faster intensification (Categories 1 to 3) and weakening (Categories 3 to 1) by about 40%. The probabilities of rapid intensification and rapid weakening have both risen in the period 2000–2018 compared to 1982–1999. A statistically significant anticorrelation is found between the lifetime maximum intensity and the following duration of the final weakening. This suggests an element of self‐regulation of TC life cycles.

Journal article

Bruneau N, Wang S, Toumi R, 2020, Long memory impact of ocean mesoscale temperature anomalies on tropical cyclone size, Geophysical Research Letters, Vol: 47, ISSN: 0094-8276

Mesoscale ocean temperature anomalies modify a tropical cyclone (TC). Through a modeling study we show that, while the maximum wind speed is rapidly restored after the TC passes a warm‐ or cold‐ (eddy size) sea surface temperature (SST) anomaly, the storm size changes are more significant and persistent. The radius of gale force winds and integrated kinetic energy (IKE) can change by more than 10% per degree and this endures several days after crossing an SST anomaly. These properties have a long memory of the impact from the ocean fluxes and depend on the integrated history of SST exposure. They are found to be directly proportional to the storm total precipitation. Accurate continuous forecast of the SST along the track may therefore be of central importance to improving predictions of size and IKE, while instantaneous local SST near the TC core is more important for the forecast of maximum wind speed.

Journal article

Sparks N, Hon KK, Chan PW, Wang S, Chan JCL, Lee TC, Toumi Ret al., 2019, Aircraft observations of tropical cyclone boundary layer turbulence over the South China Sea, Journal of the Atmospheric Sciences, Vol: 76, Pages: 3773-3783, ISSN: 0022-4928

There have been no high-frequency aircraft observations of tropical cyclone (TC) eyewall boundary layer turbulence since two flights into Atlantic hurricanes in the 1980s. We present an analysis of the first TC boundary layer flight observations in the South China Sea by the Hong Kong Observatory comprising four eyewall penetrations. We derive the vertical flux of momentum and vertical momentum diffusivity from observed turbulence parameters. We observe negative (upward) vertical fluxes of tangential momentum near the eyewall consistent with a jet below the flight level near the radius of maximum wind. Our observations of vertical momentum diffusivity support a superlinear relationship between diffusivity and wind speed at the high wind speeds in the inner-core of TCs (power-law exponent of 1.73 ± 0.20) while the few existing boundary layer hurricane observations in the North Atlantic suggest a more linear relationship.

Journal article

wang S, Toumi R, 2019, Impact of dry midlevel air on the tropical cyclone outer circulation, Journal of the Atmospheric Sciences, Vol: 76, Pages: 1809-1826, ISSN: 0022-4928

The impact of dry midlevel air on the outer circulation of tropical cyclones is investigated in idealized simulations with and without a moist envelope protecting the inner core. It is found that a dry midlevel layer away from the cyclone center can broaden the outer primary circulation and thus the overall destructive potential at both developing and mature stages. The midlevel outer drying enhances the horizontal gradient of latent heating in the rainbands and drives the expansion of the outer circulation. The moist convection at large radii is suppressed rapidly after the midlevel air is dried in the outer rainbands. An enhanced horizontal gradient of latent heating initiates a radial-vertical overturning circulation anomaly in the rainbands. This anomalous overturning circulation accelerates the radial inflow of the main secondary circulation, increases the angular momentum import, and thus increases the cyclone size. The dry air, mixed into the boundary layer from the midtroposphere, is “recharged” by high enthalpy fluxes due to the increased thermodynamical disequilibrium above the sea surface. This “recharge” process protects the eyewall convection from the environmental dry air ventilation. The proposed mechanism may explain the continuous expansion in the tropical cyclone outer circulation after maturity as found in observations.

Journal article

Wang S, Toumi R, 2018, Reduced sensitivity of tropical cyclone intensity and size to sea surface temperature in a radiative-convective equilibrium environment, Advances in Atmospheric Sciences, Vol: 35, Pages: 981-993, ISSN: 1861-9533

It has been challenging to project the tropical cyclone (TC) intensity, structure and destructive potential changes in a warming climate. Here, we compare the sensitivities of TC intensity, size and destructive potential to sea surface warming with and without a pre-storm atmospheric adjustment to an idealized state of Radiative-Convective Equilibrium (RCE). Without RCE, we find large responses of TC intensity, size and destructive potential to sea surface temperature (SST) changes, which is in line with some previous studies. However, in an environment under RCE, the TC size is almost insensitive to SST changes, and the sensitivity of intensity is also much reduced to 3% °C−1–4% °C−1. Without the pre-storm RCE adjustment, the mean destructive potential measured by the integrated power dissipation increases by about 25% °C−1 during the mature stage. However, in an environment under RCE, the sensitivity of destructive potential to sea surface warming does not change significantly. Further analyses show that the reduced response of TC intensity and size to sea surface warming under RCE can be explained by the reduced thermodynamic disequilibrium between the air boundary layer and the sea surface due to the RCE adjustment. When conducting regional-scale sea surface warming experiments for TC case studies, without any RCE adjustment the TC response is likely to be unrealistically exaggerated. The TC intensity–temperature sensitivity under RCE is very similar to those found in coupled climate model simulations. This suggests global mean intensity projections under climate change can be understood in terms of a thermodynamic response to temperature with only a minor contribution from any changes in large-scale dynamics.

Journal article

Bruneau N, Toumi R, Wang S, 2018, Publisher correction: Impact of wave whitecapping on land falling tropical cyclones, Scientific Reports, Vol: 8, ISSN: 2045-2322

Journal article

Wang S, Toumi R, 2018, A historical analysis of the mature stage of tropical cyclones, International Journal of Climatology, Vol: 38, Pages: 2490-2505, ISSN: 0899-8418

The characteristics of tropical cyclone intensity and size during the mature stage are presented. Rooted in the classic description by Herbert Riehl, the mature stage is identified as the period from the time of lifetime maximum intensity to the time of lifetime maximum size. This study is the first to analyse the global climatology of the mature stage of tropical cyclones in detail. Three basic features at the mature stage are observed: the reduction of intensity, the outward expansion of the eyewall, and the increase of tangential wind in the outer primary circulation. Globally, about a quarter of tropical cyclones undergo the mature stage. High intensity at the end of the immature stage favours the likelihood of the occurrence of the mature stage. The intensity reduction during the mature stage is considerable with nearly three-quarters of cyclones decreasing by more than 10%, which makes the conventional ‘steady-state’ presumption questionable. The increase in the radius of damaging-force wind is typically about 50 km, while the decrease in maximum wind speed is typically 20% at the mature stage. However, the average integrated kinetic energy and hence destructive potential increases substantially by about 70%. This is consistent with our finding that most of the highly damaging landfalling hurricanes undergo a mature stage. Intensity downgrades during the mature stage may be misinterpreted as they are mostly not accompanied by an overall danger reduction.

Journal article

Bruneau N, Toumi R, Wang S, 2018, Impact of wave whitecapping on land falling tropical cyclones, Scientific Reports, Vol: 8, ISSN: 2045-2322

Predicting tropical cyclone structure and evolution remains challenging. Particularly, the surface wave interactions with thecontinental shelf and their impact on tropical cyclones have received very little attention. Through a series of state-of-the-arthigh-resolution, fully-coupled ocean-wave and atmosphere-ocean-wave experiments, we show here, for the first time, thatin presence of continental shelf waves can cause substantial cooling of the sea surface. Through whitecapping there is atransfer of momentum from the surface which drives deeper vertical mixing. It is the waves and not just the wind which becomethe major driver of stratified coastal ocean ahead-of-cyclone cooling. In the fully-coupled atmosphere-ocean-wave model anegative feedback is found. The maximum wind speed is weaker and the damaging footprint area of hurricane-force winds isreduced by up to 50% due to the strong wave induced ocean cooling ahead. Including wave-ocean coupling is important toimprove land falling tropical cyclone intensity predictions for the highly populated and vulnerable coasts.

Journal article

Wang S, Fu G, Pang H, 2017, Structure Analyses of the Explosive Extratropical Cyclone: A Case Study over the Northwestern Pacific in March 2007, Journal of Ocean University of China (English Edition), Vol: 16, Pages: 933-944, ISSN: 1671-2463

The synoptic situation and mesoscale structure of an explosive extratropical cyclone over the Northwestern Pacific in March 2007 are investigated through weather station observations and data reanalysis. The cyclone is located beneath the poleward side of the exit of a 200 hPa jet, which is a strong divergent region aloft. At mid-level, the cyclone lies on the downstream side of a well-developed trough, where a strong ascending motion frequently occurs. Cross-section analyses with weather station data show that the cyclone has a warm and moist core. A ‘nose’ of the cold front, which is characterized by a low-level protruding structure in the equivalent potential temperature field, forms when the cyclone moves offshore. This ‘nose’ structure is hypothesized to have been caused by the heating effect of the Kuroshio Current. Two low-level jet streams are also identified on the western and eastern sides of the cold front. The western jet conveys cold and dry air at 800–900 hPa. The wind in the northern part is northeasterly, and the wind in the southern part is northwesterly. By contrast, the eastern jet carries warm and moist air into the cyclone system, ascending northward from 900 hPa to 600–700 hPa. The southern part is dominated by the southerly wind, and the wind in the northern part is southwesterly. The eastern and western jets significantly increase the air temperature and moisture contrast in the vicinity of the cold front. This increase could play an important role in improving the rapid cyclogenesis process.

Journal article

Wang S, Toumi R, 2016, On the relationship between hurricane cost and the integrated wind profile, Environmental Research Letters, Vol: 11, ISSN: 1748-9326

It is challenging to identify metrics that best capture hurricane destructive potential and costs. Although it has been found that the sea surface temperature and vertical wind shear can both make considerable changes to the hurricane destructive potential metrics, it is still unknown which plays a more important role. Here we present a new method to reconstruct the historical wind structure of hurricanes that allows us, for the first time, to calculate the correlation of damage with integrated power dissipation and integrated kinetic energy of all hurricanes at landfall since 1988. We find that those metrics, which include the horizontal wind structure, rather than just maximum intensity, are much better correlated with the hurricane cost. The vertical wind shear over the main development region of hurricanes plays a more dominant role than the sea surface temperature in controlling these metrics and therefore also ultimately the cost of hurricanes.

Journal article

Wang S, Toumi R, 2016, On the relationship between hurricane cost and the integrated wind profile, Environmental Research Letters, Vol: 11, ISSN: 1748-9326

It is challenging to identify metrics that best capture hurricane destructive potential and costs. Although it has been found that the sea surface temperature and vertical wind shear can both make considerable changes to the hurricane destructive potential metrics, it is still unknown which plays a more important role. Here we present a new method to reconstruct the historical wind structure of hurricanes that allows us, for the first time, to calculate the correlation of damage with integrated power dissipation and integrated kinetic energy of all hurricanes at landfall since 1988. We find that those metrics, which include the horizontal wind structure, rather than just maximum intensity, are much better correlated with the hurricane cost. The vertical wind shear over the main development region of hurricanes plays a more dominant role than the sea surface temperature in controlling these metrics and therefore also ultimately the cost of hurricanes.

Journal article

Wang S, Toumi R, Czaja A, Van Kan Aet al., 2015, An analytic model of tropical cyclone wind profiles, Quarterly Journal of the Royal Meteorological Society, Vol: 141, Pages: 3018-3029, ISSN: 1477-870X

A physically based analytic model (λ model) is presented to describe the wind profile of tropical cyclones in terms of the pressure deficit and a single shape parameter (λ). To test the λ model, an idealized full-physics numerical model is employed to provide wind-profile samples and also to show the influence of environmental temperature and the properties of initial vortices on tropical cyclone size. It is found that the λ model provides an accurate fit of the azimuthal wind profile at the top of the boundary layer. In the simulations, tropical cyclone size is sensitive to sea-surface temperature, upper tropospheric temperature and initial vortex structure. The numerical model confirms the assumed Gaussian distribution with width λ of the moist entropy in the boundary layer. A linear relationship between model cyclone size and inline image is found, in agreement with the λ model. The λ model predicts a weak relationship between tropical cyclone size and intensity, as is observed. In addition, the λ model suggests that change in tropical cyclone size should be closely related to angular momentum transport near the boundary layer, as has been found in observations. The good agreement of the λ model with the numerical model shows that the λ model could be a reasonable alternative for characterizing the wind structure of tropical cyclones with only one scaling parameter.

Journal article

Li P, Fu G, Lu C, Fu D, Wang Set al., 2012, The Formation Mechanism of a Spring Sea Fog Event over the Yellow Sea Associated with a Low-Level Jet, WEATHER AND FORECASTING, Vol: 27, Pages: 1538-1553, ISSN: 0882-8156

Journal article

Fu D, Wang S, Chen D, Pang H, Li Pet al., 2012, Comparison study between observation and simulation for sea fog over the Yellow Sea in May 2009, JOURNAL OF OCEAN UNIVERSITY OF CHINA, Vol: 11, Pages: 290-300, ISSN: 1671-2463

Journal article

This data is extracted from the Web of Science and reproduced under a licence from Thomson Reuters. You may not copy or re-distribute this data in whole or in part without the written consent of the Science business of Thomson Reuters.

Request URL: http://wlsprd.imperial.ac.uk:80/respub/WEB-INF/jsp/search-html.jsp Request URI: /respub/WEB-INF/jsp/search-html.jsp Query String: respub-action=search.html&id=00852684&limit=30&person=true