广西夏季昼夜降水特征及其差异成因分析

Characteristics of summer diurnal precipitation and the causes of its differences in Guangxi

利用广西89个国家气象站1979—2022年逐日降水观测数据,分别从昼、夜不同量级的降水量、降水日数的空间分布以及对总降水量的贡献率等方面,对广西昼夜降水变化及其差异特征进行研究,并利用再分析资料对导致广西降水昼夜差异的成因进行探究。结果表明:(1)在降水量和降水日数上,广西沿海地区昼夜均偏多,其余地区日间呈“桂南多,桂北少”,夜间呈“桂南少,桂北多”分布特征,且在不同量级降水中均有体现。(2)广西地区日间降水量对总降水量的贡献率高于夜间,但暴雨量级的贡献率则是夜间大于日间。(3)暴雨量级的夜间降水强度大于日间,且呈显著增大趋势(0.72 mm·a^(-1))。(4)夜间更强的偏南风、上升运动以及水汽辐合,利于桂北降水产生。(5)广西地区水汽主要以由南至北的经向输送为主,且夜间水汽输送强于日间。

Based on the observed daily precipitation data from 89 meteorological stations in Guangxi from 1979 to 2022,this study systematically investigates the diurnal precipitation variations and their differences in Guangxi in terms of the amount of precipitation of different magnitudes during both daytime and nighttime,the spatial distribution of the numbers of precipitation days,and the contribution rate to the total precipitation,and uses the reanalysis data to investigate the causes of the diurnal differences in precipitation in Guangxi.The results show that:(1)for precipitation and the number of precipitation days,the coastal areas of Guangxi have a higher amount of precipitation during both day and night.Apart from the coastal areas,the precipitation during daytime exhibits a pattern of“more precipitation in southern Guangxi and less in northern Guangxi”,while in nighttime shows a distribution of“less precipitation in southern Guangxi and more in northern Guangxi”.Moreover,this distribution pattern is found in the different levels of precipitation intensity.(2)Daytime precipitation contributes more significantly to the total precipitation in Guangxi than at night.However,for rainstorms,but the contribution of heavy rainfall is greater at night than during the daytime.(3)For rainstorms,the precipitation intensity at nighttime is greater than that in the daytime,with a significant increasing trend(0.72 mm·a^(-1)).(4)The stronger southerly winds,upward motion,and moisture convergence during nighttime in Guangxi are conducive to the generation of precipitation in the northern areas of Guangxi.(5)The primary moisture transport in Guangxi mainly transports in the meridional direction from south to north,with stronger water vapour transport at night than during the day.