关键词: 暴雨, 雷达回波, 地面辐合线

Abstract:

In this paper the NCEP reanalysis data，radar and surface automatic meteorological stations data were used to analyze a heavy rainstorm process on July 4 in 2012 in Shijiazhuang which could’t be forecasted at that time． The results show that the main influencing systems were upper trough and subtropical high，due to the block of the strong subtropical high，westerly trough moved to northeast，a warm shear line appeared in low level southwest airflow，and Shijiazhuang was located in north of shear line，the cloud cluster triggered by the warm shear line resulted in this rainstorm weather． The pseudo － equivalent potential temperature reached 78 ℃ and specific humidity was 14 g /kg at the level of 850 hPa，which had the certain guidance significance for the rainstorm prediction．
The torrential rain area located in the margin of the low value of TBB，and the rainstorm belongs to the tropical precipitation type． Surface convergence line maintained half hour in east of Shijiazhuang，which had positive role to strengthen radar echo． Certain correlations seem to exist between the hourly pseudo － equivalent potential temperature on the ground，the spatial distribution of vapor pressure and rainstorm area． Precipitation intensity increased when ground moisture convergence occured．

Key words: rainstorm, radar echo, surface convergence line