基于GPM探测的一次北上温带气旋降水结构特征研究
A study on the precipitation structure of a northward-moving extratropical cyclone based on GPM satellite observations
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摘要: 基于GPM卫星观测资料,分析了一次北上温带气旋降水的宏微观物理特征。通过对气旋降水区域进行象限与降水类型划分,研究了降水的精细垂直结构和雨滴谱分布特征,揭示了温带气旋降水形成的主要宏微观物理过程及其关联机制。结果表明:北上温带气旋降水主要由层云降水组成,其南部降水具有暖区降水特征,降水气团发展更为深厚、雨顶较高、强度较大,且对流活动较为活跃;北部雨带则气团浅薄,以浅对流和层云降水为主。在雨滴谱分布方面,对流降水和浅对流降水的粒子数浓度高于层云降水,对流降水的粒子有效半径亦大于层云降水,而浅对流降水的粒子有效半径则小于层云降水。整体上,粒子有效半径随雨顶高度增加而增大,而粒子数浓度与之无显著相关性。从微物理过程来看,气旋东南象限以碰并过程为主导,贡献超过60%,破碎过程次之(占比超过20%),蒸发过程影响最弱。在气旋西北象限,降水类型则成为微物理过程的主导因素,层云降水以破碎过程为主(占55.15%),而浅对流降水则主要由碰并过程主导,其比例高达89%。本研究深化了对中高纬度温带气旋降水结构的认识,相关结果可为改进数值预报模式中的云微物理与积云对流参数化方案提供理论依据。Abstract: Based on observational data from the Global Precipitation Measurement (GPM) satellite,this study investigates the macro-and micro-physical characteristics of precipitation associated with a northward-moving extratropical cyclone.The horizontal distribution and the fine-scale vertical structural characteristics of relevant physical quantities are analyzed on sectoral partitioning and precipitation-type classification within the cyclone.This approach elucidates the key macro- and micro-physical processes and their coupling mechanisms governing precipitation formation in the extratropical cyclone.Results indicate that precipitation associated with northward-moving extratropical cyclone is primarily stratiform.The southern sector exhibits typical warm-sector precipitation characteristics,with deeper convection,higher cloud tops,greater precipitation intensity,and more active convective processes.In contrast,the northern rainband is characterized by relatively shallow precipitation systems,dominated by shallow convective and stratiform types.Regarding raindrop size distribution,both convective and shallow convective precipitation exhibit higher particle number concentrations than stratiform precipitation.The effective particle radius in convective precipitation is larger than in stratiform precipitation,whereas in shallow convective precipitation it is smaller.Overall,effective particle radius increases with cloud-top height,while no significant correlation is observed with particle number concentration.In the southeastern quadrant of the cyclone,coalescence processes dominate in over 60% of precipitation samples,followed by breakup processes (exceeding 20%),with evaporation having the least influence.In contrast,within the northwestern quadrant of the cyclone,precipitation type governs the microphysical processes:stratiform precipitation is predominantly influenced by breakup processes (55.15%),while shallow convective precipitation is primarily dominated by coalescence processes (accounting for as high as 89%).This study not only enhances the scientific understanding of macro- and micro-scale characteristics and evolutionary mechanisms of extratropical cyclones in middle and high latitude regions,but also provides a theoretical foundation for improving cloud microphysical and cumulus convection parameterization schemes in numerical weather prediction models for middle and high latitude cyclones.
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