新疆一次暴雨过程的观测分析及水汽特征

The observational analysis and water vapor characteristics of a rainstorm in Xinjiang

2015年4月15—17日北疆和南疆东部出现了一场较强的暴雨过程,此次暴雨是在中亚低涡减弱成槽分裂短波、北方有冷空气补充的大尺度环流背景下产生的。观测分析显示,卫星云图相当黑体亮温TBB<-42℃区域可能出现中等强度降水、TBB<-52℃时最大小时雨强可能大于7 mm·h^(-1);乌鲁木齐风廓线雷达的反射率因子产品在大于20 d Bz的强回波出现后的30 min左右雨强增大。分析得出,水汽输送主要出现在临近暴雨前6~12 h的低层700—850 h Pa,而最大水汽通量值12 g·(cm·h Pa·s)^(-1)出现在850 h Pa,乌鲁木齐暴雨前期,出现低空急流后,5 min雨强增强,但中后期降雨强度主要取决于低空急流和中层大风速带携带的水汽及辐合抬升的强度。本文最后讨论了中国气象局沙漠气象研究所的区域数值预报模式、ECWMF和T639对这次暴雨过程的预报。

A severe rainstorm was observed in northern Xinjiang and east of southern Xinjiang from 15th to 17th of April 2005. The storm was triggered by a short wave which was separated from Middle Asian vortex with cold air supplemented from North. The result showed that heavy precipitation appeared in the area of minimum value of TBB less than -42℃. The maximum precipitation intensity was greater than 7mm h-1 while TBB was lower than -52℃. The precipitation intensity began to increase after strong reflectivity echo exceeded 20 dBz in 30 minutes from wind profiler in Urumqi. Water vapor was transported to rain belt mainly from 700 hPa to 850 hPa in 6 to 12 hours before rainstorm happened. The maximum water vapor flux was 12 g·(cm·hPa·s)-1. The 5-minute precipitation intensity was affected primarily by low-level jet in the previous stage of rainstorm. However, in later period of the low-level jet, water vapor, which was brought from large wind belt and the convergence intensity in middle level, played an important role. Finally, in the article we analyzed and discussed the forecast of the heavy rain evet in numerical prediction model of the Institute of Desert Meteorology in CMA, ECWMF and T639.