江苏南部汛期降水日变化特征分析

利用江苏南部20个气象观测站2008—2012年汛期(5—10月)逐小时降水资料,应用降水频率来分析了江苏南部地区降水日变化基本特征和区域差异。研究表明:降水日变化特征地域性差异较强,西部站、东部站和东北沿海站都存在一定的特征差异。东部站降水量的最大值主要出现在下午和傍晚;西部站降水量主峰值出现在下午,并且在清晨和夜间还有两个次峰值;东北沿海站呈现出午前、午后的双峰值形式。2008—2011年降水量下午高值区有先减弱后增强并提前的趋势,而上午的高值区有总体减弱并推迟的特征。2011年后有明显减弱的趋势。江苏南部总体来说,短时强降水(大于20和25 mm/h)在16—19时出现主峰值,07—09时也有相对较小的次峰值。

Characteristics analysis on diurnal variation of precipitation in flood season of southern Jiangsu

By using hourly precipitation data in rainy season(May-October) from 20 meteorological stations in southern Jiangsu during 2008-2012, the basic characteristics and regional differences of diurnal variation of summer rainfall in southern Jiangsu were analyzed, based on precipitation frequency. Results show that a strong regional difference exists in the diurnal variation characteristics of precipitation, especially in the western, eastern and northeastern coastal stations. The maximum value of precipitation at the eastern stations basically occurs in the afternoon and evening; at the western stations, the main peak happens in the afternoon and two secondary peaks are in the early morning and evening, respectively; at the northeastern coastal stations, a double peak presents before and after midday. During 2008-2011,the annual precipitation in the high-value areas in the afternoon tends to weakening first and then is followed by an enhancing and shifting to an earlier time, while in the morning, it presents overall weakening-delaying; after 2011, a weakening trend occurs obviously. Overall, in southern Jiangsu, the peak of short-term heavy rainfall (especially magnitude more than 20 and 25 mm/h) occurs at 16-19 in the afternoon, and a relatively small peak is observed at 07-09 in the morning.