干侵入对江淮流域一次强飑线过程的作用分析

Analysis of Impact of Dry Intrusion in a Strong Squall Line Process in Eastern China

利用NCEP/NCAR再分析资料、雷达资料、FY-2E卫星资料等,对2014年7月30—31日发生在江淮流域的一次强飑线天气过程进行综合分析,并着重分析了干侵入对此次飑线过程的作用。结果表明:中层阶梯槽引导高层干冷空气向下入侵后叠加在低层暖湿气流之上,增强了大气不稳定,不稳定能量累积;低空切变线促使不稳定能量释放,是此次飑线的重要触发机制。对干侵入的分析结果表明:此次飑线过程中,干侵入来源于高空槽后下沉气流,干侵入底部风场调整使得飑线在移动过程中由东西向转为了南北向。在飑线发展过程中,干侵入范围扩大、强度增强;干侵入使飑线发生区域中高层大气相对湿度降低约50%,增强了大气不稳定。干侵入底部的低相当位温空气与飑线内部高相当位温空气混合是飑线长时间维持的重要原因。

Using the NCEP/NCAR reanalysis data, radar and satellite data in this paper the synoptic characteristics of a strong squall line process in eastern China during 30th-31st July, 2014 were analyzed. The mechanism of dry intrusion in the process were revealed. The results indicate that：the mid-level stairs-shape trough introduced dry-cold air from the high-level superimposed on the low-level warm air, the atmospheric instability enhanced and unstable energy accumulated; low level shear line prompted unstable energy released, it was an important trigger mechanism for the squall line. The analysis results of dry intrusion show that： in this squall line process, dry intrusion originated from downdraft behind the high-level trough, wind adjustment at the bottom of dry intrusion urged the squall line to change the moving direction. Dry intrusion was expanded and strengthened during the development of squall line;Dry intrusion made air over the squall line came colder and dryer and increased atmospheric instability. Low equivalent temperature air under dry intrusion mixed with high equivalent temperature air inside the squall line, it is the important reason for squall line to maintain for a long time.