河池市春季气候背景及降雨特征分析

Analysis of Climate Background and Rainfall Characteristics of Hechi City in Spring

统计分析1986~2015年30a河池市春季降雨时空分布特征,并采用欧洲中心再分析资料分析春季(3~5月)河池市气候环流背景,为进一步研究春季降雨预报指标奠定基础。结果表明:春季500hPa东亚中高纬基本为一槽一脊形势,西太平洋副热带高压逐渐西伸北抬,南支系统逐渐活跃,河池市上空由平直偏西气流转受西南气流影响;850hpa由偏西北气流转为西南气流,水汽输送加大;冷空气活动区域逐渐往北往西收缩,强度减弱,并经华北、江淮以偏东路径影响河池,河池盛行偏东风,雨日渐多,雨量渐增。在大尺度环流背景下,河池市春季降雨概率呈现夜雨大于日雨,且3月最为明显,5月差异最小。空间上,夜雨由北向南递减,日雨则自东向西减少,以3、4月最明显,至5月呈均匀分布特征。

The spatial and temporal distribution characteristics of spring rainfall in Hechi City from 1986 to 2015 are analyzed.The climate circulation background of Hechi City in spring(March to May)is analyzed by using the Eurocenter reanalysis data,which lays a foundation for further study of spring rainfall forecast index.The results show that 500 hPa in spring is basically a trough-ridge situation in the middle and high latitudes of East Asia,the western Pacific subtropical high gradually extends northwest,the southern branch system is gradually active,and the southwest airflow influences the flow over Hechi City from a straight westward direction.850 hPa changes from a northwest direction to a southwest direction,and the water vapor transport increases.The cold air gradually shrinks northward and westward,and weakens its intensity.It influences the river basin by the eastward route of North China and Jianghuai.The east wind prevails in the river basin,and the rainfall is increasing day by day.Under the background of largescale circulation,the probability of spring rainfall in Hechi City shows that night rainfall is greater than day rainfall,especially in March,and the smallest difference appears in May.Spatially,night rain decreases from north to south,while daily rain decreases from east to west,with the most obvious in March and April,and from May,it presents a uniform distribution.