天津地区三次低涡暴雨过程的诊断分析

利用地面实况资料及NCEP再分析资料(1°×1°),选取2016年、2010年及2011年发生在天津市的3次强降水天气过程,分析其天气形势及水汽条件,并应用湿位涡理论对3次暴雨天气进行了诊断分析。分析结果表明:3次暴雨过程均发生在典型的东高西低的环流形势下,低空低涡是主要的影响系统之一。低涡的动力结构及水汽条件的差异对应不同的降水强度。正涡度区强度越强、维持时间越长,降水强度越大。2016年过程水汽通量散度明显强于另两次过程的,与其降水强度相匹配。湿位涡的时空演变可以很好地描述天津地区暴雨的发生发展。天津上空MPV_1负值区标志着不稳定能量的急剧增加,MPV_1负值区出现在降水发生前3 h至6 h,提前预示了天津地区暴雨天气的发生。MPV_1正值区对应强降水的区域。过程降水前MPV_2绝对值的激增,表明大气的斜压性增强,有利于气旋性涡度发展。MPV_2绝对值的激增基本同步于降水的发生。

Diagnostic Analysis of Three Heavy Rainfall Processes With Vortex in Tianjin

Based on the conventional ground observational data and NCEP reanalysis data(1°×1°), 3 heavy rainfall processes in Tianjin in 2016, 2010 and 2011 were chosen, the synoptic background and water vapor conditions of the 3 processes were analyzed, and the 3 heavy rainfall processes were diagnostic analyzed using the theory of moist potential vorticity. The results showed: the 3 rainstorm processes occurred in a typical circulation pattern of east high west low, low altitude vortex is one of the main influencing systems. There were upper and lower jet in the 3 rainfalls, but the positions of jet were different. The difference of the dynamic structure and water vapor conditions of the vortex corresponded to the intensity of precipitation in varying degrees. The stronger intensity of the positive vorticity region and the longer duration indicated the greater precipitation intensity.The divergence of water vapor flux in 2016 was obviously stronger than that of the other 2 processes, which matched the precipitation intensity. Temporal and spatial evolution of moist potential vorticity corresponded well to the occurrence and development of heavy rainfall. The sharp increase of instability energy above Tianjin signed by negative area of MPV1, the negative area appeared in advance 3 h to 6 h before the rainfall, and it predicted the occurrence of heavy rainfall in Tianjin. Positive area of MPV1 corresponded to the region of heavy rainfall.There were the sharp increases of MPV2 before these 3 processes of rainfall.Negative value increase of MPV2 indicated greatly enhances of the baroclinic, and it was favorable to the development of cyclone vorticity. The sharp increases of MPV2 value was basically synchronized with the occurrence of precipitation.