关键词: 区域自动站, 极端降水, 低层气流, 垂直结构, 地形作用

Abstract: Based on the intensified hourly rainfall observation data of regional automatic weather stations, the characteristics of extreme precipitation from May to September during 2008-2017 in southwestern Hubei was analyzed by using percentile method. Satellite cloud photograph TBB data and NCEP reanalysis data with 0.5°×0.5° spatial resolution were adopted to analyze the causes of typical cases. The results are as follows: (1) The degrees of extreme precipitation at different stations were not comparable because of large difference in threshold ranges between hourly heavy rainfall and daily extreme precipitation. The stations with high frequency of hourly heavy rainfall and heavy rainstorm mainly distributed around the mountains with topographic convergence and uplift. Hourly heavy rainfall mainly occurred during the period of 00:00-03:00 and 16:00-19: 00. (2) Most of the extreme precipitation in southwestern Hubei occurred near Hefeng with large altitude difference. Low-level jet flow and topographic effect caused the back propagation of mesoscale convection system during the eastward migration process, which led to long duration of precipitation and large accumulated rainfall. (3) The thermodynamics and vertical structures were different for the extreme precipitation processes in different periods. For warm sector extreme precipitation in June, thermal effect dominated and the upper layer systems developed before the lower. Dynamic effect was main for extreme precipitation in September, in which frontal zone was obvious, and the whole system strengthened.

Key words: regional automatic weather stations, extreme precipitation, low level air flow, vertical structure, topographic effect