关键词: 夜雨现象, 年变化, 动力条件, 水汽条件, 气候趋势

Abstract:

Based on the precipitation data of 603 stations in China and the ERA5 hourly reanalysis data from 1967 to 2016,this paper analyzed characteristics of temporal and spatial variations of nocturnal precipitation in China from the perspective of nocturnal precipitation rate and nocturnal precipitation frequency. Results showed that: the stations with nocturnal precipitation were mainly distributed in the Southwest China,Northwest China,Huang Huai River Basin,Central China,Beijing?Tianjin?Hebei,northwest of South China and south of Northeast China. The nocturnal precipitation appeared most obviously in Sichuan,Tibet,Guizhou,Xinjiang and Qinghai provinces. In these areas,the nocturnal precipitation rate reached 60%,even up to 80% for individual stations,and the nocturnal precipitation frequency rate reached 55%,even up to 60% for individual stations in the whole year and all seasons. Significant seasonal variation can be seen in both spatial distribution of average nocturnal precipitation rate and nocturnal precipitation frequency rate. As for the seasonal distribution of nocturnal precipitation in China,stations with nocturnal precipitation were mainly distributed in the Southwest China,Northwest China,East China,Central China,northeast Inner Mongolia,Beijing?Tianjin?Hebei,northwest of South China and south of Northeast China in spring. During the summer,the area where this phenomenon occurred shrunk,with distribution in the Southwest China,most parts of central and southwest Xinjiang,a few areas of Gansu and Qinghai provinces,and parts of Beijing?Tianjin?Hebei,Shandong,Henan,Liaoning provinces. Almost most areas among China were covered by stations with nocturnal precipitation in autumn and winter. The paper split stations with obvious nocturnal precipitation into N?type,V?type,M?type,W?type and Λ?type respectively according to the monthly variation of average nocturnal precipitation rate and nocturnal precipitation frequency rate. These types have different characteristics of monthly variation: for N?type,the relatively high value and low value of nocturnal precipitation rate or nocturnal precipitation frequency rate commonly appeared in spring and summer respectively. Main features for V?type were relatively high value and low value of nocturnal precipitation rate or nocturnal precipitation frequency rate commonly appeared in winter and summer respectively. M?type showed significant high value of nocturnal precipitation rate or nocturnal precipitation frequency rate commonly appeared in spring and autumn,and it turned relatively low commonly in summer and winter,meanwhile W?type was classified by the relatively high value of rate commonly appeared in summer and winter and the relatively low value commonly appeared in spring and autumn. This paper also classified Λ?type by its obvious peak and valley of nocturnal precipitation rate or nocturnal precipitation frequency rate in summer and winter respectively. For the issue of distribution,N?type stations were mainly distributed in Yunnan?Guizhou Plateau,eastern foothills of the Tibetan Plateau was a typical V?type station area,while the M?type stations were mainly distributed in the Sichuan Basin. There was a consistency between monthly variation of differences between night and day of dynamic conditions and water vapor conditions affecting precipitation and the monthly variation of nocturnal precipitation rate and nocturnal precipitation frequency rate in corresponding sites,clear consistency could be found in N?type stations,which had a relatively peak value of differences between night and day of dynamic conditions in spring and relatively low value in summer. V?type region also showed this consistency in the trend of these two measures with lowest value in summer and largest in winter. Same fact appeared in M?type region with peak value in spring. Among stations with obvious nocturnal precipitation,the nocturnal precipitation rate and nocturnal precipitation frequency rate increased significantly in Nuomu Hong in Qinghai province,with nocturnal precipitation became more and more obvious. Nocturnal precipitation gradually weakened in Alashankou in Xinjiang,Haiyang in Shandong,Ruoergai and Seda in Sichuan,Nyingchi in Tibet,Nanyue in Hunan,Baoshan in Shanghai,Pingtan in Fujian and other stations,with significantly reduced nocturnal precipitation rate and nocturnal precipitation frequency rate. The nocturnal precipitation rate changed by about 1%~3% every ten years,while the nocturnal precipitation frequency rate changed by about 0.4%~1.5% every ten years. the fluctuation range of nocturnal precipitation rate with years was larger than nocturnal precipitation frequency rate in these stations.

Key words: nocturnal precipitation, annual variation, dynamic conditions, water vapor conditions, climate trends