近50年深圳龙舟水暴雨环境参量统计分析

A Statistical Analysis of the Environmental Parameters for Heavy Rains During the Dragon⁃boat Rain Periods over the Past 50 Years in Shenzhen

利用深圳国家基本气象站雨量数据和香港地区(45003)探空资料,对1973—2020年近50年龙舟水期间(每年5月21日—6月20日)深圳暴雨(12 h雨量≥30 mm)过程中表征温湿条件、能量和动力条件的物理量进行统计分析,基于25百分位提取了龙舟水暴雨过程的关键环境参数阈值。结果表明:(1)表征水汽条件的大气可降水量PW、500 hPa温度露点差(t-td)500、850 hPa温度露点差(t-td)850以及表征能量条件的K指数对龙舟水期间深圳暴雨的发生具有更明显的指示作用,暴雨发生前的大气可降水量充沛,整层水汽均接近饱和,大气能量充足;(2)对比分析了白天和夜间暴雨发生前的环境参量特征,在龙舟水期间,当08:00大气环境满足大气可降水量PW≥62 mm、(t-td)500≤3.5℃、(t-td)850≤2.8℃、K指数≥35℃,有利于白天出现暴雨;当20:00大气可降水量PW≥61 mm、(t-td)500≤3.1℃、(t-td)850≤3.4℃、K指数≥34℃,有利于夜间暴雨发生。

Based on the rainfall data from a national basic meteorological observation station in Shenzhen and radiosonde data from Hong Kong region(site No.:45003),this work statistically analyzed the physical quantities that depict the temperature and humidity,energy and dynamics during heavy rains(with 12 h rainfall amount≥30 mm)in the recent 50 Dragon⁃boat Rain periods(spanning annually from May 21 to June 20)from 1973 to 2020,and extracted the thresholds of key environmental parameters with these heavy rains based on 25 percentiles.The results are shown as follows.(1)The heavy rains during the Dragon⁃boat Rain periods can be better indicated by atmospheric precipitable water(PW),500 hPa temperature⁃dew point difference((t-td)500),850 hPa temperature⁃dew point difference((t-td)850)and the K index for depicting energy conditions.Prior to these heavy rains,the PW was sufficient in the atmosphere,water va⁃por was near the point of saturation,and the atmosphere was full of energy.(2)From a comparison of the characteristics of environmental parameters prior to the heavy rain between the day and the night,it is known that when PW≥62 mm,(t-td)500≤3.5℃,(t-td)850≤2.8℃and the K index≥35℃at 08:00,it is favorable for daytime heavy rains to take place,and if PW≥61 mm,(t-td)500≤3.1℃,(t-td)850≤3.4℃and the K index≥34℃,it is likely that nocturnal heavy rains will happen.