doi:  10.3878/j.issn.1006-9895.1712.17126
一次飑线过程对流稳定度演变的诊断分析

Diagnostic analysis of convective stability evolution during a process of squall line
摘要点击 156  全文点击 37  投稿时间:2017-02-27  修订日期:2017-12-05
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基金:  公益性行业(气象)科研专项(GYHY201406029,GYHY201306043)、国家重点基础研究发展计划(2013CB430105),国家自然科学基金项目(41175060)
中文关键词:  飑线,对流不稳定,位势稳定度,位势散度
英文关键词:  Squall , Convective instability, Potential stability, Potential divergence
           
作者中文名作者英文名单位
周围Zhou Wei南京信息工程大学
包云轩Bao Yunxuan南京信息工程大学
冉令坤Ran Lingkun中国科学院大气物理所
王勇Wang Yong中国人民解放军94826部队
引用:周围,包云轩,冉令坤,王勇.2018.一次飑线过程对流稳定度演变的诊断分析[J].大气科学
Citation:Zhou Wei,Bao Yunxuan,Ran Lingkun,Wang Yong.2018.Diagnostic analysis of convective stability evolution during a process of squall line[J].Chinese Journal of Atmospheric Sciences (in Chinese)
中文摘要:
      针对2016年5月2日发生在华东地区的一次飑线过程,利用WRF模式进行高分辨率数值模拟。在成功模拟飑线发生、加强和移动的基础上,对此次过程中对流不稳定特征以及引起对流稳定度变化的原因进行诊断分析。结果表明:(1)在降水发生前,低层大气表现为对流不稳定;降水发生后,对流不稳定能量得到释放,大气趋于稳定。为了分析引起对流稳定度变化的原因,推导了局地直角坐标系中相当位温垂直梯度的倾向方程,其中位势散度是引起位势稳定度局地变化的主要强迫项。在弱降水区,低层位势散度为负值,有利于增强位势不稳定;强降水区及其前沿为位势散度正值区,倾向于抑制位势不稳定。在强降水区低层,位势散度的主要分量为垂直风切变项,代表垂直风切变和大气湿斜压性的综合作用;高层的主要分量为散度项,代表水平散度和位势稳定度的耦合作用。(2)位势散度能综合表征降水区上空垂直风切变、大气湿斜压性、水平辐合辐散和大气位势稳定度变化等特征,因而与降水联系紧密。本文利用位势散度对飑线降水进行数值释用预报,结果表明,位势散度与小时观测降水在时间和空间上吻合较好,对降水区有一定的指示意义,可以为飑线降水业务预报提供参考。
Abstract:
      The Weather Research and Forecast (WRF) model with the high resolution was used to simulate the rainfall during a process of squall line that occurred in the eastern China on May 2, 2016. Based on successful simulation of the squall line process occurrence, strengthening and evolution, the convective instability characteristics and the causes of convective stability variation were analyzed. The results were showed as follows: (1) before the rainfall coming, the atmosphere is convective unstable but after the rainfall appeared, the atmosphere tends to be stable due to the release of energy. In order to ascertain the physical cause of convective stability, the vertical potential temperature gradient’s tendency equation in local rectangular coordinate was deduced and the potential divergence was the main coerce term in the equation. In the weak rainfall area, the potential divergence in lower atmosphere was negative, which was conducive to enhance potential instability. In the strong precipitation area, the potential divergence was positive and tended to inhibit potential instability. In the lower level of rainfall area, the main component of the potential divergence was vertical wind shear item, which was on behalf of the vertical wind shear and the atmospheric moist baroclinicity. While in the higher level, its main component was divergence item which meant the coupling effect of the horizontal divergence and potential stability. (2) Based on the ability of potential divergence describing vertical wind shear、atmospheric baroclinicity、horizontal divergence and the variation of atmospheric potential stability, in this paper, we tried to using potential divergence to forecast precipitation during the squall line. The results displayed that potential divergence were in good agreement with the observed one hour precipitation in time and space, which had instructive meaning to the rainfall area, therefore it can provide an important reference for precipitation forecasting during the process of squall line in operation.
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