豫东地区短时强降水时空分布特征及物理量指标分析

Analysis of Synoptic Characteristics of Short-time Heavy Precipitation and the Physical Quantity Index in Eastern Henan Province

利用1985-2018年汛期(5-9月)豫东地区20个国家站小时降水资料和2011-2018年同期豫东地区区域自动站观测数据、NCEP(1°×1°)再分析资料、高空地面观测资料等,统计分析了该区域小时雨强分别≥20 mm/h、≥30 mm/h和≥50 mm/h的短时强降水时空分布特征,结果发现:豫东地区近34年汛期平均年降水量为458.9~577.5 mm/a,短时强降水次数为72.8次/a;2000年是短时强降水多发年份,≥20 mm/h的雨强出现158次,是常年平均次数的1.17倍;主汛期的7-8月是不同强度短时强降水多发时期,34年来共计发生≥20 mm/h的短时强降水1821次,占同强度短时强降水总次数(2476次)的近74.0%;在短时强降水的日变化中,05时是不同强度短时强降水多发时段,20时为次多发时段。对不同环流背景影响下短时强降水过程的水汽、动力、热力及能量等物理量作统计分析,低槽型短时强降水过程的动力条件优于其他两个类型的,850 hPa涡度平均值达3.8×10-5s^-1,700 hPa垂直速度平均值达-0.36 Pa·s^-1;副高边缘型短时强降水过程不稳定能量条件优势显著,850 hPa假相当位温平均值达354.1 K,500-850 hPa假相当位温差的平均值达-17.80℃,K指数平均值为38.1℃、CAPE值平均值为2075.0 J·kg^-1;而台风倒槽型短时强降水过程则在水汽输送方面更具优势,850 hPa比湿平均值为15.5 g·kg^-1,整层可降水量达70.0 mm。

Based on the hourly precipitation data from 20 national-level weather stations from May to September during 1985-2018,the regional automatic station observation data in the same periods of 2011-2018 in the eastern part of Henan province,the NCEP 1°×1°reanalysis data and the upper-air surface observations,this paper statistically analyzes the temporal and spatial distribution characteristics of short-time heavy precipitation with hourly rain intensities≥20 mm/h,≥30 mm/h and≥50 mm/h.The results show that,in the 34 years,the annual average precipitation in flood season in eastern Henan was 458.9-577.5 mm/a,and the short-time heavy rainfalls occurred 72.8 times/a.In 2000,such heavy rainfalls were seen the most,with 158 times of hourly precipitation≥20 mm/h,which is 1.17 times of the normal.From July to August in the main flood season,short-time heavy rain events of different intensities take place at the highest frequency.During the 34 years,the short-time heavy precipitation≥20 mm/h occurred 1821 times,accounting for 74.0%of the total precipitation of the same intensity(2476 times).In the diurnal variation of short-time heavy precipitation,such intense rainfalls tend to occur at 05 o’clock most,and then is at 20 o’clock.In addition,statistical analysis is made on the physical quantities such as water vapor,dynamic condition,thermodynamic condition and energy during the process of short-time heavy precipitation under the influence of different circulation backgrounds.The dynamic conditions of the low-trough type short-time heavy precipitation process are better than those of the other two types.The average vorticity at 850 hPa is 3.8 h-5s-1,and the average vertical velocity at 700 hPa is-0.36 Pa·s^-1.The unstable energy conditions in the process of the short-time heavy precipitation of marginal subtropical high type have significant advantages.The average value of the 850 hPa pseudo-equivalent potential temperature is 354.1 K,the average value of the 500-850 hPa pseudo-equivalent potential temperature difference is-17.80℃,the average value of K index is 38.1℃,and the average value of CAPE is 2075.0 J·kg^-1.However,the short-time heavy precipitation of typhoon inverted trough type has more advantages in water vapor transport.The average value of specific humidity at 850 hPa is 15.5 g·kg^-1,and the precipitable water of the whole layer is up to 70.0 mm.