川东北一次西北气流型强冰雹天气的成因分析

利用常规气象资料和NCEP／NCAR 1°×1° 6h再分析资料，从大气环流形势、物理量场等方面对2007年4月29日发生在川东北地区的一次强冰雹天气过程的成因进行了分析。结果表明：此次西北气流型冰雹天气是在低能量环境场条件下发生的；冰雹天气发生前12h内降雹区的对流有效位能激增、午后下垫面强烈加热对大气不稳定性增强的作用显著；大气层结对流不稳定、湿对称不稳定、充足的水汽以及干线（露点锋）的存在为此过程提供了有利条件。

Cause Analysis on a Heavy Northwest Airflow Type Hailstorm Events Occurred in the Northeast of Sichuan Province

Based on the conventional observations and NCEP/NCAR 1°×1° 6 h reanalysis data, the cause of a severe hailstorm event occurred in the northeast of Sichuan province on 29 April 2007 is analyzed from the circulation situation and several physics fields. The results show that this hailstorm event occurred under the northwest airflow pattern and low-energy conditions. The sharp increase of convective available potential energy and the strong heating of under laying surface in the afternoon significantly influence to increase the atmosphere instability in the hail area during the 12 h ahead this event happened. The atmosphere convective instability, moist symmetry instability, sufficient moisture and the dry line provide the favorable conditions for this event occurring.