沿江苏南一次伴随"高架雷暴"的暴雪天气成因分析

利用沿江苏南地面气象站监测资料以及NCEP/NCAR再分析资料,探讨了2013年2月18-19日一次罕见伴随雷暴的暴雪天气过程的成因机制。结果表明:700 hPa强盛的暖湿气流与925 hPa显著的偏东风急流交汇,形成了"暖盖"与"冷垫"稳定叠置并持续维持的锋生机制,为此次暴雪的发生发展提供了成熟的动力热力条件,在淞附增长作用下,形成较强降雪。强降雪落区与假相当位温密集带有很好的对应关系。对饱和湿位涡的进一步诊断分析表明,此次伴随暴雪出现的雷暴是较典型的冷区"高架雷暴",它出现在条件性对称不稳定的环境中。通过等熵分析揭示了雷暴的触发机制:暖湿气流沿着锋面从低层爬升到600~650 hPa,与冷空气相遇触发了本次雷暴。

Cause analysis of a snowstorm case with elevated thunderstorm in southern Jiangsu province

Based on the meteorological observation data and NCEP/NCAR reanalysis data,this paper analyzes the characteristics and causes of an infrequent snowstorm process accompanied by thunderstorm occurred from 18 to 19 February 2013.Results show that the strong 700 hPa southwest airflow and the obvious 925 hPa eastern jet,which act as the warm cover and the clod pad,provide energetic motivation condition for the heavy snowfall.Favorable upper and lower pumping configuration of divergence is weighted towards the long-duration snowfall.The snowfall is intensified by the riming effect.The snow center corresponds quite well to the concentrated belt of pseudo-equivalent temperature.The thunderstorm that occurrs in cold situation is a typical elevated thunderstorm in this case.The further diagnostic analysis of saturated moist potential vorticity shows that the thunderstorm occurrs in the conditional symmetric instability situation.The isentropic analysis reveals the trigger mechanism of the thunderstorm:The warm airflow climbs along the cold front from low layer to 600-650 hPa and meets the cold air,which triggers the thunderstorm.