Roles of Upper-Level Descending Inflow in Moat Development in Simulated Tropical Cyclones with Secondary Eyewall Formation  

作　　者：Nannan QIN Liguang WU 

机构地区：[1]Nanjing Joint Institute for Atmospheric Sciences,Nanjing 210041,China [2]Shanghai Typhoon Institute,China Meteorological Administration,Shanghai 200030,China [3]Department of Atmospheric and Oceanic Sciences and Institute of Atmospheric Sciences,Fudan University,Shanghai 200438,China [4]Innovation Center of Ocean and Atmosphere System,Zhuhai Fudan Innovation Research Institute,Zhuhai 518057,China

出　　处：《Advances in Atmospheric Sciences》2024年第6期1100-1114,共15页大气科学进展（英文版）

基　　金：supported by the National Natural Science Foundation of China(Grant Nos.42192552,42192551,42150710531,42175016,and 42075072);the Shanghai Typhoon Research Fund(Grant No.TFJJ202207);the Basic Research Fund of CAMS(Grant No.2023Y010)。

摘　　要：This study investigated the effects of upper-level descending inflow(ULDI)associated with inner-eyewall convection on the formation of the moat in tropical cyclones(TCs)with secondary eyewall formation(SEF).In our numerical experiments,a clear moat with SEF occurred in TCs with a significant ULDI,while no SEF occurred in TCs without a significant ULDI.The eyewall convection developed more vigorously in the control run.A ULDI occurred outside the inner-eyewall convection,where it was symmetrically unstable.The ULDI was initially triggered by the diabatic warming released by the inner eyewall and later enhanced by the cooling below the anvil cloud.The ULDI penetrated the outer edge of the inner eyewall with relatively dry air and prevented excessive solid-phase hydrometeors from being advected further outward.It produced extensive sublimation cooling of falling hydrometeors between the eyewall and the outer convection.The sublimation cooling resulted in negative buoyancy and further induced strong subsidence between the eyewall and the outer convection.As a result,a clear moat was generated.Development of the moat in the ongoing SEF prevented the outer rainband from moving farther inward,helping the outer rainband to symmetrize into an outer eyewall.In the sensitivity experiment,no significant ULDI formed since the eyewall convection was weaker,and the eyewall anvil developed relatively lower,meaning the formation of a moat and thus an outer eyewall was less likely.This study suggests that a better-represented simulation of inner-eyewall convective structures and distribution of the solid-phase hydrometeors is important to the prediction of SEF.

关 键 词：tropical cyclone secondary eyewall formation upper-level descending inflow eyewall convection 

分 类 号：P444[天文地球—大气科学及气象学]