华南一次飑线过程线状对流模态变异机理研究
投稿时间: 2016-05-28  最后修改时间: 2016-06-03  点此下载全文
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作者单位E-mail
康兆萍 中国气象科学研究院灾害天气国家重点实验室 zpingkang@163.com 
林永辉 中国气象科学研究院灾害天气国家重点实验室 linyh@camscma.gov.cn 
基金项目:国家重点基础研究发展计划(973计划)
中文摘要:利用高时空分辨率的地面测观资料、探空资料、NCEP再分析资料和多普勒天气雷达资料,并结合中尺度数值模式WRF对2013年5月15日发生在广西广东地区的一次强飑线过程进行分析研究,着重分析了中尺度对流系统(MCS)由平行型(PS)模态到拖尾型(TS)模态的转变过程及机理。此次飑线过程发生于高层弱辐散区,500hPa有明显短波槽东移发展,850hPa有切变线和低空暖湿急流,地面有冷锋和低压倒槽。西侧初始对流发展为PS型MCS模态,成熟期无雷暴高压。东侧减弱的初始对流与西侧PS型MCS合并发展成为TS型MCS模态。数值模拟结果显示PS型模态具有平行于对流线的气压梯度力和加速度分量,该分量导致了平行于对流线的风分量。TS型模态中,平行于对流线的气压梯度力和加速度很小,而垂直于对流线的气压梯度力和加速度很大,正是由于平行于对流线的加速度分量的消失和垂直于对流线的加速度分量的增强促使对流线内部相对系统流场由平行向转变为垂直向,导致MCS模态由PS型转为TS型。
中文关键词:平行型,拖尾型,气压扰动,飑线
 
The mechanism of transition of convective mode of a squall line in South China
Abstract:Based on high spatial and temporal resolution surface observational data, sounding data, NCEP reanalysis data, Doppler radar data, and high resolution data produced by WRF model, the severe squall line event that occurred over Guangxi and Guangdong Provinces on 15 May 2013 is analyzed. The paper mainly focuses on the transition process and mechanisms of mesoscale convective system(MCS) mode from PS mode to TS mode. The squall line formed in the region which is under the divergence area at 200-hPa, ahead of the eastward trough at 500-hPa, between the northwestern shear line and the southeastern low-level jet at 850-hPa, near the surface cold front and in the area of surface inverted trough. The western convection organizes into PS mode without thunderstorm high The eastern weakening convection strengthens again and then combines the western PS MCS to convert to TS mode. The simulation results show that, in PS mode, line-parallel pressure gradient force, acceleration and relative line-parallel stream are great. In TS mode, line-parallel pressure gradient force acceleration and relative line-parallel stream are very weak, but line-perpendicular pressure gradient force and acceleration are quite strong. It is the decrease of line-parallel acceleration and the increase of line-perpendicular acceleration results in the transformation from PS mode to TS mode.
keywords:Parallel stratiform, Tailing stratiform, Pressure perturbation, Squall line
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