水平湍流混合对莫拉克(2009)台风强度及结构的影响  

The impact of horizontal turbulent mixing on simulation of structure and intensity of Typhoon Morakot(2009)

作　　者：张璐[1] 张熠[1] 周博闻 Zhang Lu;Zhang Yi;Zhou Bowen(Key Laboratory of Mesoscale Severe Weather/Ministry of Education,School of Atmospheric Sciences,Nanjing University,Nanjing,210023,China)

机构地区：[1]中尺度灾害性天气教育部重点实验室,南京大学大气科学学院,南京210023

出　　处：《南京大学学报（自然科学版）》2020年第5期616-629,共14页Journal of Nanjing University（Natural Science）

基　　金：国家自然科学基金(41775057);国家重点研究发展计划(2017YFC1501601);国家自然科学基金(41875011)。

摘　　要：在台风的发生、发展过程中,水平湍流混合是重要的物理过程,该过程的参数化方案对台风个例的数值模拟结果有很大影响.研究通过调整WRF(Weather Research and Forecasting Model)模式水平湍流参数化方案中的Smagorinsky系数Cs(Smagorinsky Coefficient)控制水平湍流混合的强弱,对比分析了水平湍流混合强度在台风莫拉克(2009)数值模拟中对台风强度和结构的影响.结果表明:水平湍流混合对莫拉克台风路径的模拟没有显著影响,但对台风的最大强度有显著影响,随着Cs增大台风强度减弱,热力场分析表明过大的水平混合不利于台风暖心的维持.从轴对称风场特征来看,Cs变化的影响并非集中在边界层中,台风中上层的风场均发生了改变,但边界层中变化更大,随着Cs增大最大风速半径外扩.从雨带和对流的发展特征来看,Cs越小越有利于模拟出单点发展的对流胞,但这些对流胞不易组合发展为有组织的对流带,而Cs过大时,对流胞出现涡丝化发展形态而发展为平滑的长雨带,减弱了雨带内的对流强度但使对流区的分布更趋于对称化,且过大的水平交换作用不利于雨带精细结构的模拟.The horizontal turbulent mixing, which is an important physical process in the genesis and evolution of tropical cyclones(TC),will affect the numerical simulation results of TC. By adjusting the Smagorinsky coefficient(Cs) in horizontal turbulence parameterization scheme in WRF(Weather Research and Forecasting) model, this research performes six numerical experiments of a real TC case(Morakot 2009)and examines the influence of horizontal turbulent mixing on TC intensity and structure. The results show that horizontal turbulent mixing has no significant effect on the simulated TC′s track,but will significantly influence TC′s maximum intensity,as Cs increases the intensity decreases. Thermal field analysis shows that excessive horizontal mixing between the inner core and outer periphery is not conducive to the maintenance of TC′s warm core. The vertical extent that horizontal mixing influences is not only concentrate in the boundary layer but also to the upper model layer,but the degree of influence is greater in the boundary layer. As Cs increases,the radius of maximum wind speed extends. Analysis of the asymmetric structure of rainbands and convection in TC shows that the smaller Cs is more favorable to the simulation of grid-scale isolated convective cells, but these convective cells are not easy to merge into organized convective belts. When the value of Cs increases, the convective cells appear vortex filament development morphology and will stretch to a long rainband,which weakens the intensity of grid-scale convection and is not conducive to the simulation of the fine-scale structure of rainbands,but makes the TC structure more symmetrical.

关 键 词：水平湍流混合 台风数值模拟 对流 螺旋雨带 

分 类 号：P44[天文地球—大气科学及气象学]