南京大学学报(自然科学版) ›› 2020, Vol. 56 ›› Issue (5): 616–629.doi: 10.13232/j.cnki.jnju.2020.05.002

• • 上一篇    

水平湍流混合对莫拉克(2009)台风强度及结构的影响

张璐,张熠(),周博闻   

  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
  • 收稿日期:2020-06-05 出版日期:2020-09-30 发布日期:2020-09-29
  • 通讯作者: 张熠 E-mail:yizhang@nju.edu.cn
  • 基金资助:
    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)

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

Lu Zhang,Yi Zhang(),Bowen Zhou   

  1. Key Laboratory of Mesoscale Severe Weather/Ministry of Education, School of Atmospheric Sciences, Nanjing University, Nanjing, 210023, China
  • Received:2020-06-05 Online:2020-09-30 Published:2020-09-29
  • Contact: Yi Zhang E-mail:yizhang@nju.edu.cn

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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.

关键词: 水平湍流混合, 台风数值模拟, 对流, 螺旋雨带

Abstract:

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 Csincreases 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.

Key words: horizontal turbulent mixing, numerical simulation of TC, convection, spiral rainband

中图分类号: 

  • P44

图1

(a)本文实验模拟区域，外层水平网格距为9 km，内层网格距为3 km，同时叠加了中国台湾气象台最佳路径资料提供的莫拉克（2009）台风路径与控制实验（CS0.25）模拟路径；（b）观测资料与控制实验模拟的台风海平面最低气压（单位：hPa）与距离海平面10 m最大风速（单位：m?s-1）对比，图中实线为观测结果，虚线为控制实验结果"

图2

8月6日00时至8月10日00时的台风96 h累积降水分布特征（单位：mm）(a)观测降水分布；(b)控制实验模拟降水分布"

图3

莫拉克（2009）台风六组对比实验模拟的2009年8月6日00时至8月10日00时的路径和强度(a) TC tradk,(b) minimum sea level pressure(unit: hPa),(c) maximum wind speed of 10 m height (m?s-1）"

图4

六组实验中台风在登陆台湾前和登陆台湾后所能达到的10 m最大风速值（单位：m?s-1）Blue triangles and red dots represent the maximum wind speed before (during 0000 UTC August 6 to 2300 UTC August 7) and after (during 0000 UTC August 8 to 0000 UTC August 10) landfall on Taiwan,respectively."

图5

8月6日17时45分至18时15分期间30 min时间平均的轴对称风场，填色图代表径向风，等值线代表切向风(a) CS0,(b) CS0.1,(c) CS0.25,(d) CS0.5,(e) CS0.75,(f) CS1"

图6

各实验累积降水分布特征（单位：mm）：(a~f)为8月6日00时至8月10日00时台风96 h累积降水量；(g~i)为8月6日00时至8月8日00时台风登陆台湾前48 h的累积降水；(j~l)为8日00时至10日00时台风登陆台湾后48 h累积降水"

图7

观测及CS0，CS0.25及CS1三实验中模拟的最大雷达回波反射率分布图(a，b)对应观测结果，(c~h)对应模拟结果；图中左栏对应于8月6日18时,右栏对应8月8日00时"

图8

经过图7台风中心的南北向垂直剖面上的位温（填色）、30 dBZ雷达回波轮廓线（黑色实线）及剖面上的环流（箭头）(a~c) corresponds to 1800 UTC on August 6,(d~f) corresponds to 0000 UTC on August 8"

图9

8月6日18时及8月8日00时9 km CS0.25和3 km CS0.75组合方案中台风最大雷达反射率的对比图(a) 9 km CS0.25 at 1800 UTC August 6,(b) 3 km CS0.75 at 1800 UTC August 6(c) 9 km CS0.25 at 0000 UTC August 8,(d) 3 km CS0.75 at 0000 UTC August 8"

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