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梅雨锋前线状中尺度对流系统成熟阶段的空气垂直运动分析

ISSN号：1004-4965
期刊名称：热带气象学报
时间：2014
页码：687-699
分类：P458.121.1[天文地球—大气科学及气象学]
作者机构：[1]中国气象科学研究院灾害天气国家重点实验室,北京100081
相关基金：国家973项目（2012CB417202）;国家自然科学基金（41175049、 41221064）;国家科技支撑项目（2012BAC22B00）;中国气象科学研究院基本科研业务费（2012Y001）共同资助
相关项目：江淮流域梅雨MCS结构特征与对流-层云降水过程研究

作者：宫宇|罗亚丽|

关键词：梅雨锋暴雨, 显式对流模拟, 中尺度对流系统, 空气垂直运动, Meiyu frontal torrential rainfall, cloud-permitting simulation, mesoscale convective system, vertical motion of air

中文摘要：

2007年7月8日清晨,中尺度对流系统（MCS）沿着梅雨锋南缘准东西向切变线形成和发展,造成了淮河流域特大暴雨.本文综合分析高分辨率的雷达回波和地面观测资料,较严格验证了1.1kin分辨率的数值模拟结果,进而研究了模拟的MCS成熟阶段的深对流（DC）和层云降水区域（RST）空气垂直运动（w）及其预报方程倾向项的分布.DC区域内以强空气上升运动为主,最强上升运动在对流层中层（～6 km）,在低层（＜1.5 km）空气上升和下沉运动并存;RST区域中高层弱上升、低层（4～5 km以下）弱下沉.w预报方程各项中,空气扰动密度浮力项（B1）、扰动气压梯度力项（PGA）和水凝物拖曳项（B2）起着主要作用.在DC区域,低层（1.5 km以下）B1项有助于高θse空气上升和低θse空气下沉,PGA有助于空气上升运动,即热力和动力作用共同影响着新的对流的形成;2～ 10km高度,水物质的相变造成的热力作用支持着DC区域内强烈的上升运动;云顶附近B1为负、PGA为正,这可能是因为空气弱的上升运动导致绝热冷却和长波辐射的冷却作用.与DC区域相比,RST区域内各项的强度比较弱,在～5 km高度以下,雨滴蒸发冷却作用是导致空气下沉运动的最重要的因子;5～ 12kin高度,从DC区域卷出到RST区域的暖湿空气及凝华所释放的潜热是造成正的浮力作用（B1＞0）的主要原因;云顶附近则与DC的情况类似.

英文摘要：

During the early morning hours of 8 July 2007,a mesoscale convective system （MCS） developed near the southern edge of a Meiyu front,causing torrential rainfall over the Huaihe river valley.Structural features of the MCS are studied using high-resolution surface data and radar reflectivity.Air vertical velocity （w） in the MCS＇s mature stage is investigated using a 24 h cloud-permitting simulation with the finest grid spacing of 1.11 km which is validated by comparing with the observations.The major conclusions are as follows.The MCS consists of deep convective （DC） and stratiform raining （RST） regions.In the DC regions,the air vertical motion is mainly ascending with the maximum w at the mid-troposphere （～ 6 km）.At the low altitudes （below 1.5 km）,environmental high-θse air ascends and convectively generated low-θse air descends.In the RST,air ascends weakly at the mid-to-high altitudes （above 5km） and descends weakly below 4 ～ 5 km altitudes.The perturbation air density buoyancy term （B 1）,vertical pressure gradient force term （PGA） and hydrometer loading term （B2） play important roles in the predictive equation of w.In the DC regions below the ～ 1.5 km altitude,both the B1 and PGA terms help form new convection at the leading edge.At 2 ～ 10 km altitudes,latent heating induced by changes in water phases supports the strong upward motion of air in the DC regions.Near the cloud tops,B 1 is negative and PGA is positive possibly because of longwave radiative cooling and adiabatic cooling in association with weak upward motion of air.Compared to the DC regions,the RST regions see smaller values of B 1,PGA and B2.Below ～ 5 km,B 1 and B2 are negative while PGA is positive in the RST regions,suggesting that cooling due to rain drops evaporation is the major contributing factor for the weak air descent.At 5 ～ 10 km altitudes in the RST regions,detrainment of positively buoyant air from the DC regions to the RST regions and the subsequent depositional heating result i