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How Does Tropical Cyclone Size Affect the Onset Timing of Secondary Eyewall Formation？

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Journal of Meteorological Research 2018年第1期32卷 124-134页

作者： Liang GUAN xuyang ge Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters/Key Laboratory of Meteorological Disaster Nanjing University of Information Science & Technology Nanjing 210044 Shanghai Meteorological Science and Technology Service Center Shanghai 200030

By using idealized numerical simulations, the impact of tropical cyclone size on secondary eyewall formation（SEF） is examined. Both unbalanced boundary layer and balanced processes are examined to reveal the underlying mechanism. The results show that a tropical cyclone（TC） with a larger initial size favors a quicker SEF and a larger outer eyewall. For a TC with a larger initial size, it will lead to a stronger surface entropy flux, and thus more active outer convection. Meanwhile, a greater inertial stability helps the conversion from diabatic heating to kinetic ***, the progressively broadening of the tangential wind field will induce significant boundary layer imbalances. This unbalanced boundary layer process results in a supergradient wind zone that acts as an important mechanism for triggering and maintaining deep convection. In short, different behaviors of balanced and unbalanced processes associated with the initial wind profile lead to different development rates of the secondary eyewall.

关键词： secondary eyewall formation tropical cyclone size surface entropy flux

Comparison of Controlling Parameters for Near-Equatorial Tropical Cyclone Formation between Western North Pacific and North Atlantic

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Journal of Meteorological Research 2021年第4期35卷 623-634页

作者： Changhao LU xuyang ge Melinda PENG Key Laboratory of Meteorological Disaster of Ministry of Education/Joint International Research Laboratory of Climate and Environment Change/Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters Nanjing University of Information Science&TechnologyNanjing 210044China University of Colorado Colorado SpringColorado 80918USA

In this study,the differences in spatial distribution and controlling parameters for the formation of near-equatorial tropical cyclones(NETCs)between the western North Pacific(WNP)and the North Atlantic(NA)are *** exhibit distinctive spatial variabilities in different *** the past few decades,the majority of NETCs took place in WNP while none was observed in *** mechanism behind such a distinguishing spatial distribution difference is analyzed by using statistical *** is noted that the dynamical variables such as low-level relative vorticity and vertical wind shear(VWS)are likely the primary controlling *** with NA,larger low-level vorticity and smaller VWS appear over *** increase of vorticity attributes a lot to the turning of northeast trade *** in WNP tend to occur in the areas with VWS less than 9 m s^(-1),while the VWS in NA generally exceeds 10 m s^(-1).On the other hand,the sea surface temperature in the near-equatorial region of both of the two oceans exceeds 26.5℃and the difference of mid-level moisture is not significant;thus,thermal factors have little contribution to the distinction of NETC activities between WNP and *** oscillation(ISO)and synoptic-scale disturbances in WNP are also shown to be more favorable for NETC *** NETCs were generated in ISO active ***-scale disturbances in WNP obtain more energy from the mean flows through the barotropic energy conversion *** overall unfavorable thermal and dynamic conditions lead to the absence of NETCs in NA.

关键词： near-equatorial tropical cyclone(NETC) cyclogenesis genesis potential index(GPI)

季风低压诱发2018年8月广东特大暴雨过程分析

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大气科学学报 2024年第1期47卷 95-107页

作者：黄玉蓉黄绮君郭炳瑶葛旭阳陈明诚南京信息工程大学气象灾害教育部重点实验室/气象灾害预报预警与评估协同创新中心江苏南京210044

利用NCEP/FNL再分析资料和中尺度数值模拟方法探讨2018年8月27日—9月1日季风低压环境下广东特大暴雨过程的形成成因。利用扰动天气图方法分析发现,季风低压和西南急流为此次广东暴雨过程提供了有利的水汽条件和能量条件。熵变零线位置... 详细信息

利用NCEP/FNL再分析资料和中尺度数值模拟方法探讨2018年8月27日—9月1日季风低压环境下广东特大暴雨过程的形成成因。利用扰动天气图方法分析发现,季风低压和西南急流为此次广东暴雨过程提供了有利的水汽条件和能量条件。熵变零线位置与降水落区位置有较好的对应,零线处能量有最大累积,有利于暴雨的发生发展,对预报暴雨降水落区有一定的指示意义。为进一步验证季风低压的影响机制,构建不同季风低压尺度的敏感性试验,即通过滤去季风低压环流中的扰动分量来改变季风低压的强度。结果表明:暴雨强度与季风低压尺度和强度存在密切的关系。当季风低压强度较强时,暴雨过程总雨量强;当季风低压强度较弱时,降水大为减少甚至无降水。诊断分析指出,能量螺旋度指数能够较好反映出不同情形下降水发生发展,在季风低压背景下,暴雨区能量螺旋度指数较大,降水强度较强。反之,随着季风低压强度减弱,能量螺旋度指数减小,降水减弱。

关键词：季风低压暴雨能量螺旋度水汽条件

Dependence of Tropical Cyclone Intensification on the Latitude under Vertical Shear

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Journal of Meteorological Research 2018年第1期32卷 113-123页

作者： Mingyu BI xuyang ge Tim LI Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters/Key laboratory of Meteorological Disaster Nanjing University of Information Science &Technology International Pacific Research Center/Department of Atmospheric Sciences University of Hawaii at Manoa

The sensitivity of tropical cyclone（TC） intensification to the ambient rotation effect under vertical shear is investigated. The results show that the vortices develop more rapidly with intermediate planetary vorticity, which suggests an optimal latitude for the TC development in the presence of vertical shear. This is different from the previous studies in which no mean flow is considered. It is found that the ambient rotation has two main effects. On the one hand,the boundary layer imbalance is largely controlled by the Coriolis parameter. For TCs at lower latitudes, due to the weaker inertial instability, the boundary inflow is promptly established, which results in a stronger moisture convergence and thus greater diabatic heating in the inner core region. On the other hand, the Coriolis parameter modulates the vertical realignment of the vortex with a higher Coriolis parameter, favoring a quicker vertical realignment and thus a greater potential for TC development. The combination of these two effects results in an optimal latitude for TC intensification in the presence of a vertical shear investigated.

关键词： tropical cyclone intensification vertical shear Coriolis parameter

Impacts of the Diurnal Cycle of Solar Radiation on Spiral Rainbands

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Advances in Atmospheric Sciences 2016年第9期33卷 1085-1095页

作者： Shunwu ZHOU Yue MA xuyang ge Key Laboratory of Meteorological Disaster of Ministry of Education/Joint International Research Laboratory of Climate and Environment Change/Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters Nanjing University of Information Science and TechnologyNanjing 210044 Shanghai Climate Center Shanghai 200030

Based on idealized numerical simulations, the impacts of the diurnal cycle of solar radiation on the diurnal variation of outer rainbands in a tropical cyclone are examined. It is found that cold pools associated with precipitation-driven downdrafts are essential for the growth and propagation of spiral rainbands. The downdrafts result in surface outflows, which act as a lifting mechanism to trigger the convection cell along the leading edge of the cold pools. The diurnal cycle of solar radiation may modulate the diurnal behavior of the spiral rainbands. In the daytime, shortwave radiation will suppress the outer convection and thus weaken the cold pools. Meanwhile, the limited cold pool activity leads to a strong modification of the moisture field, which in turn inhibits further convection development.

关键词： solar shortwave radiation tropical cyclone spiral ralnbands diurnal cycle

Sensitivity of Tropical Cyclone Intensification to Inner-Core Structure

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Advances in Atmospheric Sciences 2015年第10期32卷 1407-1418页

作者： ge xuyang XU Wei ZHOU Shunwu Key laboratory of Meteorological Disaster Collaborative Innovation Center on Forecast and Evaluation of Meteorological DisastersNanjing University of Information Science & Technology State Key Laboratory of Severe Weather Chinese Academy of Meteorological Sciences

In this study, the dependence of tropical cyclone （TC） development on the inner-core structure of the parent vortex is examined using a pair of idealized numerical simulations. It is found that the radial profile of inner-core relative vorticity may have a great impact on its subsequent development. For a system with a larger inner-core relative vorticity/inertial stability, the conversion ratio of the diabatic heating to kinetic energy is greater. Furthermore, the behavior of the convective vorticity eddies is likely modulated by the system-scale circulation. For a parent vortex with a relatively higher inner-core vorticity and larger negative radial vorticity gradient, convective eddy formation and radially inward propagation is promoted through vorticity segregation. This provides a greater potential for these small-scale convective cells to self-organize into a mesoscale inner-core structure in the TC. In turn, convectively induced diabatic heating that is close to the center, along with higher inertial stability, efficiently enhances system-scale secondary circulation. This study provides a solid basis for further research into how the initial structure of a TC influences storm dynamics and thermodynamics.

关键词： tropical cyclone intensification inner-core structure

Simulated Sensitivity of the Tropical Cyclone Eyewall Replacement Cycle to the Ambient Temperature Profile

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Advances in Atmospheric Sciences 2017年第9期34卷 1047-1056页

作者： Xulin MA Jie HE xuyang ge Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters Key Laboratory of Meteorological DisasterNanjing University of Information Science and Technology

In this study, the impacts of the environmental temperature profile on the tropical cyclone eyewall replacement cycle are examined using idealized numerical simulations. It is found that the environmental thermal condition can greatly affect the formation and structure of a secondary eyewall and the intensity change during the eyewall replacement cycle. Simulation with a warmer thermal profile produces a larger moat and a prolonged eyewall replacement cycle. It is revealed that the enhanced static stability greatly suppresses convection, and thus causes slow secondary eyewall formation. The possible processes influencing the decay of inner eyewall convection are investigated. It is revealed that the demise of the inner eyewall is related to a choking effect associated with outer eyewall convection, the radial distribution of moist entropy fluxes within the moat region, the enhanced static stability in the inner-core region, and the interaction between the inner and outer eyewalls due to the barotropic instability. This study motivates further research into how environmental conditions influence tropical cyclone dynamics and thermodynamics.

关键词： tropical cyclone eyewall replacement cycle ambient temperature profile

Modulation of High-Latitude Tropical Cyclone Recurvature by Solar Radiation

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Journal of Meteorological Research 2023年第6期37卷 802-811页

作者： Jiawei LING xuyang ge Melinda PENG Qijun HUANG Key Laboratory of Meteorological Disaster of Ministry of Education Joint International Research Laboratory of Climate and Environment ChangeCollaborative Innovation Center on Forecast and Evaluation of Meteorological DisastersNanjing University of Information Science&TechnologyNanjing210044China University of Colorado Colorado Springs Colorado SpringsColorado80918USA

In this study,idealized simulations are conducted to investigate potential influences of solar radiation on the tropical cyclone(TC) recurvature at higher *** indicate that TC track is sensitive to the seasonal variation of radiative forcing at higher *** the absence of a background flow,TCs at higher latitudes tend to recurve(remain northwestward) in the cold(warm) *** feature is an additional aspect of the so-called intrinsic recurvature property of TC movement at high ***,the greater meridional gradient of temperature in the cold season due to solar radiative forcing would induce a larger thermal wind,which affects the upper-level anticyclonic circulation and associated *** structure changes of TC,mainly at upper-levels,modulate the steering flow for TC,leading to a higher probability of TCs at higher latitudes to recurve in the cold season than in the warm season.

关键词： tropical cyclone motion solar radiative forcing higher latitude thermal wind

Urban Impact on Landfalling Tropical Cyclone Precipitation:A Numerical Study of Typhoon Rumbia(2018)

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Advances in Atmospheric Sciences 2023年第6期40卷 988-1004页

作者： Xinguan DU Haishan CHEN Qingqing LI xuyang ge KLME/ILCEC/CIC-FEMD Nanjing University of Information Science and TechnologyNanjing 210044China School of Atmospheric Sciences Nanjing University of Information Science and TechnologyNanjing 210044China

Coastal urban areas are prone to serious disasters caused by landfalling tropical cyclones(TCs). Despite the crucial role of urban forcing in precipitation, how fine-scale urban features impact landfalling TC precipitation remains poorly understood. In this study, high-resolution ensemble simulations of Typhoon Rumbia(2018), which crossed the Yangtze River Delta urban agglomeration, were conducted to analyze the potential urban impact on TC precipitation. Results show that the inner-core rainfall of Rumbia is strengthened by approximately 10% due to the urban impact near the landfall,whereas minor differences in outer-core rainfall are found when the urban impact is excluded. Further diagnostic analyses indicate that low-level upward motion is crucial for precipitation evolution, as both co-vary during landfall. Moreover, the frictionally induced upward motion plays a decisive role in enhancing the rainfall when the urban impacts are *** surface friction can decelerate the tangential wind and therefore destroy the gradient balance and strengthen the radial wind within the boundary layer and thus can enhance upward motion. This study demonstrates that urban surface friction and related physical processes make the most significant contribution to landfalling TC rainfall enhancement.

关键词： landfalling tropical cyclone urban agglomeration quantitative diagnosis rainfall physical mechanisms surface friction