关键词: 首场暴雨, 气候特征, 影响系统, 环流形势

Abstract:

Based on the hourly and daily precipitation data of 122 weather stations in Shandong Province during 1985-2014, the climatic characteristics of the first rainstorm were analyzed. Combined the synoptic charts from Micaps system during 1999-2014, the influence systems and circulation situations of the first rainstorm in Shandong were summarized and analyzed. The results showed that the first rainstorm usually occurred from April to May in Shandong Province, and the local rainstorm dominated, followed by large-scale rainstorm. The daily variation of the first rainstorm was significant, and the rainfall was strong at night and in the early morning, while that was weak in the daytime. The first rainstorms frequently occurred in Peninsula and the southwest of Shandong, but the distribution characteristics in two areas were different. The frequency of the first rainstorm was higher in the Peninsula area and the daily and hourly maximum precipitation was less, while that was highest in southwestern Shandong and the daily and hourly maximum precipitation was also bigger. It is found out that the main synoptic systems influencing the first rainstorm in Shandong included the extratropical cyclone and vortex shear line. The local and large-scale rainstorms frequently caused by the cyclone and most likely happened in Peninsula and the southwest of Shandong, while the regional rainstorms were mainly caused by the vortex shear line and usually happened in northwestern and central Shandong. The locations of ground cyclone and vortex shear line on 850 hPa were very important indicators to forecast the drop area of the first rainstorm. The rainstorms frequently appeared in the north of cyclone trough and the intersection area between the vortex shear line on 850 hPa and the southeast airflow of ground cyclone. The dynamic and water vapor factors of the first rainstorm under the cyclones influence dominated, while the thermal instability was key factor for the vortex shear line influence system. In addition, the sufficient water vapor from the southwest warm and moist airflow, invasion of cold air or convergence with warm air were necessary to produce the first rainstorm.

Key words: the first rainstorm, climatic characteristics, influence system, circulation situation