两次极端强降水风暴双偏振参量特征对比分析

Contrast analysis of dual-polarization signatures for the two extreme rainfall storms

基于济南S波段双偏振多普勒天气雷达(CINRAD/SA-D)探测资料,并结合区域自动气象站以及常规观测资料,对2020年8月5日和6日山东两次极端强降水风暴环境条件进行对比分析,并重点分析莘县王庄集和兖州大安风暴的双偏振参量特征。结果表明:两次极端强降水天气均具有较高的K指数和较大的对流有效位能(Convective Available Potential Energy,CAPE),湿层厚,垂直风切变中等偏弱,但6日强降水低层垂直风切变和相对风暴螺旋度明显偏强。风暴气流结构有明显差异:王庄集和大安风暴分别表现为倾斜上升和气旋性旋转气流结构,前者风暴顶辐散强而后者较弱,从而导致前者风暴顶高度及差分相移率(K_(DP))柱高度较高。不同高度微物理结构有差异:-10℃层高度之上,两者以固态粒子为主,而王庄集风暴含有更加深厚、丰富的霰粒子,-20~-10℃层还有一定浓度较小的液态粒子;-10℃层高度以下,两者以浓度较高的液态粒子为主,而王庄集风暴含有一定数量的冰相粒子。风暴低层测站周围差分反射率(Z_(DR))、K_(DP)和相关系数(Correlation Coefficient,CC)大致相当,Z_(DR)适中,粒子大小适中,K_(DP)和CC较大,风暴降水主体液态雨滴浓度较高,含水量丰富,从而产生高强度降水。

Based on the Ji’nan S-band dual-polarization Doppler weather radar (CINRAD/SA-D) data,combined with automatic weather station data and conventional observation data,comparative analysis of the environmental conditions are made,and emphasis is laid on the analysis of dual-polarization signatures for the Wangzhuangji storm and Da’an storm,which are short for the two extreme rainfall storms separately occurring at Wangzhuangji county of Shenxian and Da’an county of Yanzhou,Shandong on 5 and 6 August 2020.The results show that:the two extreme heavy rain occurred in the conditions of high K index,large convective available potential energy (CAPE),deep wet layer,and moderately weak vertical wind shear.In contrast,the storm relative helicity (SRH) is evidently larger for the extreme rainfall event on 6 in August.The flow structures of the storms are significantly different:the Wangzhuangji storm tilts upward and intensively diverges at high-level inducing higher storm top and specific differential phase K_(DP)column,while Da’an storm performs as cyclonic rotation with weaker high-level divergence.The microphysical structure varies at different levels:for the both two storms,there are high concentration of solid (liquid) particles separately above (below) -10℃ layer.But Wangzhuangji storm has more abundant graupels abov e-10℃ layer,a few element of liquid particles from -20℃ to -10℃ layer,and a certain amount of ice particles below -10℃ layer.The two storms exhibit comparable dual-polarization characteristics with moderate differential reflectivity Z_(DR),bigger K_(DP)and correlation coefficient (CC) at low-level,which indicate that the rainfall storms constructed with abundant moderate particle size liquid raindrops are rich of water favorable for extreme rainfall.