川渝盆地主汛期短时强降水事件日变化特征研究

利用四川盆地和重庆地区1980-2012年主汛期(5-9月)基本站小时降水观测资料,分析了短时强降水事件降水量、频次和强度的日变化特征,研究了短时强降水事件日峰值位相和空间分布特征,事件极值降水日变化和持续时间等分布特征,得出以下主要结论:1)川渝盆地短时强降水事件开始时间的日变化上(01:00-24:00时,北京时间,下同),表现为"V"型结构下典型夜间峰值位相特征;结束时间的日变化上,表现为多个峰值型结构分布.强降水事件持续时间的日变化上,频次和降水量均呈双峰型结构,频次极大峰值出现在3h,而强度上随着持续时间的延长,呈现逐渐增加的趋势;2)短时强降水事件极值开始时间空间分布上,极大频次和极大降水量出现在20:00-01:00时内,主要分布在盆地南部和西部大部分地区;日峰值频次结束时间主要发生在20:00-01:00时和08:00-13:00时两个时段内,主要分布于盆地南部、中部和西部大部分地区;3)短时强降水事件极值降水的日变化上,降水量和频次呈现单峰型结构,白天多为短时间(2~4h)强降水事件出现极值,而傍晚开始至第二天清晨,持续2~10h强降水事件出现极值均有发生;强降水事件极值降水持续时间日变化,1~24h内呈单峰型结构,峰值出现在2h.

Diurnal Variation of the Short-Duration Strong Rainfall Events in Sichuan and Chongqing During the Main Flood Season

Based on the qualified hourly rainfall database of 123 stations in Sichuan province and Chongqing municipality during the major flood period from 1980 to 2012, diurnal variations in amount, frequency and intensity of short-duration strong rainfall events are investigated, their diurnal peak phases and spatial distribution features are studied and their diurnal changes of maximum rainfall and duration hours are analyzed. The main conclusions are as follows. The diurnal variations of beginning time of short-duration strong rainfall events show a single active peak structure with a typical night peak phase from 01:00 to 24:00 Beijing time (BJT), and the ending time of the strong rainfall events show a multi-active peaks structure. For the diurnal variations in duration hours of short-duration strong rainfall events, both their frequency and amount are characterized by a double-peaked structure, with the maximum frequency happening at lasting 3 hours. The intensity gradually increases by the lasting time. The beginning time of maximum frequency and rainfall amount of short-duration strong rainfall events mainly occur between 20:00 and 01:00 and are largely distributed in the southern and western regions of the Basin, and the ending time of diurnal peak of frequency mostly happens from 20:00 to 01:00 and from 08:00 to 13:00 and is located in the southern, central and western regions of the Basin. Diurnal variations in the maximum rainfall, the frequency and the amount of short-duration strong rainfall events at different happening time show a single active peak structure. The maximum rainfall with short lasting hours (2-4 h) occur at day time, yet the maximum precipitation with lasting 2 to 10 hours all happen between the nightfall and the next day morning. The diurnal variations of maximum rainfall show a single active peak structure at 3 h.