1980-2012年5-9月川渝盆地小时强降水特征研究

摘要

利用四川和重庆123个气象观测站1980-2012年小时降水资料,分析川渝地区主汛期5-9月小时强降水频次、强度和持续性等时间演变和空间分布特征.结果表明,≥20、≥30和≥50 mm· h-1三种强度阈值强降水时间演变上,1980-2012年年际和日变化具有较好的一致性,三种强降水年平均频次分别为504、184和28次.≥20mm· h-1强降水空间分布上,在山地地形动力辐合抬升,以及盆地西部较大的地形梯度作用下,≥20 mm· h-1强降水高频次区主要分布于盆地西北部的龙山山脉、西南部雅安及乐山周围与盆地过渡区.≥20 mm· h-1强降水频次的日峰值空间分布上,盆地南部主要出现在20:00-01:00(北京时,下同),而盆地中部、北部和东部主要在02:00-07:00.持续不同小时时间尺度的强降水事件日变化上,具有双峰型结构,午后为第一个降水峰值,20:00至第二天07:00为第二个峰值,白天多为短时间(2～6 h)强降水事件,而傍晚开始至第二天清晨,持续2～18 h强降水事件均有发生.不同开始时间强降水事件的强度与频次和降水量具有一致性的日变化特征,呈现单峰型结构,峰值主要发生在18:00-06:00,且不同开始时间事件频次和降水量空间分布上,白天(09:00-20:00)相对于夜间(21:00-08:00)偏小,即夜间强降水事件特征表现明显.%Based on the qualified hourly precipitation data of 123 stations in Sichuan Province and Chongqing City from 1980 to 2012,the multiple spatio-temporal distribution characteristics of the frequency,the intensity and the duration of hourly heavy rainfall (HHR) during main flood season from May to September are investigated.The main conclusions are as follows.The annual variation and diurnal variation of frequency during 1980-2012 are nearly identical at the thresholds above 20 mm,30 mm and 50 mm per hour.The average annual frequency of HHR is 504,184 and 28 respectively.According to the dynamic convergence lifting over mountain terrain and the forcing of large mountain gradient in the west of Sichuan and Chongqing Basin,the high frequency areas of HHR at the thresholds above 20 mm per hour distribute in Longshan Mountains in the northwest of the basin and the transition zone between the surrounding area of Ya'an and Leshan and the southwest of basin.The diurnal peak of frequency mainly happens between 20:00 BT and 01:00 BT in the south of basin and between 02:00 BT and 07:00 BT in the central,north and east of the basin.The diurnal variation of different hours shows double active peaks with the first peak after the noon and the second peak between 20:00 BT and the next 07:00 BT.The events of short duration (2-6 h) mostly occur in the day time,yet the events of lasting 2 to 18 hours all happen between the nightfall and the next morning.The intensity,frequency and precipitation amount of the events of HHR at distinct beginning time are characterized by similar daily variation with the single active peak happening between 18:00 BT and 06:00 BT.The accumulating rainfall and the frequency of the HHR events are less during the day time (09:00-20:00 BT) than over night (21:00-08:00 BT),which means the HHR events are remarkable at night time.