江南一次持续性暴雨过程中线状中尺度对流系统模态转换机理研究
投稿时间: 2017-04-28  最后修改时间: 2017-05-25  点此下载全文
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作者单位E-mail
王雪 中国气象科学研究院 wxue121@126.com 
林永辉 中国气象科学研究院 linyh@camscma.gov.cn  
基金项目:973项目(2012CB417200),气象行业专项(GYHY201306004)
中文摘要:本文利用地面加密观测资料、探空资料、NCEP再分析资料和多普勒天气雷达组网拼图资料,结合中尺度数值模式WRF输出资料,研究了2014年6月20-21日发生在江南地区的一次持续性暴雨过程中中尺度对流系统(MCS)的演变过程、结构特征及模态转变机理。此次持续性暴雨过程发生在200hPa高层辐散区、500hPa东移发展的短波槽前侧、850hP切变线与低空暖湿急流之间的不稳定区。MCS演变过程中组织模态发生转变,对流东移发展中形成拖尾型(TS)MCS,后逐渐转变为平行型(PS) MCS。环境风场上,TS型MCS表现为垂直对流线的相对入流,弓状回波北侧有气旋生成,PS型MCS低层表现为垂直对流线的相对入流,中高层表现为平行对流线的相对入流。TS型MCS中,强对流区位于正扰动气压带,形成垂直作用于对流线的气压梯度力,导致相对入流垂直对流线;而在平行对流线方向上,扰动气压变化小,平行相对气流较弱,整体呈现为较强的垂直向后的相对气流;在PS型MCS中,气压扰动整体表现为西南正气压扰动与东北负气压扰动的分布特征,在西南东北向气压梯度力作用下,形成平行对流线向后的相对入流,导致MCS组织模态的转变。
中文关键词:拖尾型,平行型,持续性暴雨,相对入流
 
The mechanism of transition of linear mesoscale convection system mode in a continuous rainstorm process in Jiangnan Area
Abstract:Based on intensive surface observational data, sounding data, NCEP reanalysis data, Doppler radar data, and high resolution data produced by WRF model, the evolution process, organizational structure and modal transformation mechanism of the mesoscale convective system (MCS) during the process in a continuous rainstorm in Jiangnan area from 20 June to 21 June 2014 were studied. The continuous rainstorm process formed in the region which is under the divergence area at 200-hPa, ahead of the eastward trough at 500-hPa, between the shear line and the wet and warm low-level jet at 850-hPa. Organizational modal transformation occurs during MCS evolution. In the eastward development, convection forms Tailing stratiform type (TS) MCS and gradually changed to Parallel stratiform type (PS) MCS. In the environmental wind field, the relative inflow of TS MCS is vertical convection line, and the cyclone is generated on the north side of the arcuate echo. The circulation distribution of PS MCS is that the lower level is the relative inflow of the vertical convection line and the middle and upper layers show the relative inflow of the parallel convection line. In TS MCS, the strong convection zone is located in the positive disturbance zone, forming vertical force acting on the convection line and resulting in a relative inflow perpendicular to the convection line. But in the parallel convection line direction, disturbance pressure change is small. So the parallel relative airflow is weak, and the overall presentation of the relative airflow is a vertical convection line. In the PS MCS, the overall performance of the pressure distribution characteristics is the southwest positive pressure disturbance and northeast negative pressure disturbance. The pressure gradient force in the northeast and northwest forms the relative inflow of the parallel convection line, which leads to the transformation of MCS microstructure.
keywords:Tailing stratiform, Parallel stratiform, Continuous rainstorm, Relative inflow
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