Research On Temporal And Spatial Characteristics Of Precipitation In South China

In recent years,as an essential part of the meteorological and hydrological cycle,precipitation has undergone some changes because of global climate change.The spatial and temporal distribution of precipitation restricts the social and economic development of a region.It is of great significance for the flood control and drought mitigation of the region and the effective use of water resourcesBased on the latest daily meteorological observation data in South China from 1967 to 2018,the spatiotemporal characteristics of the precipitation in South China over the past 52 years was studied.By a non-parametric trend analyzing method,it was found that only 8% of the stations in South China had a significant increase in annual rainfall.There is no significant positive trend at any weather station.Monthly rainfall showed the most apparent decreasing and increasing trends in April and November,respectively.During the whole flooding season,the monthly rainfall of the weather stations along the coastal areas showed almost no significant changing trend.The spatial distribution of the annual rainfall gradually decreases toward the inland area with the central and coastal areas of Guangdong province as the high-value rainfall center.The spatial distribution of annual average rainfall day is opposite to the spatial distribution of annual rainfall.The spatial distribution of monthly rainfall varies with seasons.The rainfall in the inland area of South China mainly concentrates from April to September,but the month with high rainfall in Hainan is relatively lagging behind that for the inland area.Due to data availability,the distribution of the diurnal rainfall is only focused on Shenzhen.The night rainfall is lower than that during the day,in spring and summer,the diurnal rainfall peaks appear before and after noon,respectively.In autumn,the diurnal rainfall distribution is bimodal,with peaks occurring before and after noon time.By using the empirical orthogonal function decomposition method,the dominant rainfall patterns of monthly rainfall of the meteorological stations in South China were analyzed.The results show that the two main monthly rainfall modes have strong annual signals.The spatial interpretation rate of the first mode is 60.09%,and their spatial distribution is basically consistent with the average annual rainfall distribution.The monthly average time coefficients have the maximum and minimum values in June and December.The spatial interpretation rate of the second mode is 11.41%,and its spatial distribution is gradually decreasing from south to north.The maximum and minimum values of the monthly average time coefficients are in September and March,respectively.Both the third and fourth modes have strong semi-annual signals,and the spatial interpretation rate is less than 5%.Finally,based on the reanalysis data,the large-scale circulation background of the spatial and temporal distribution of precipitation in South China is analyzed from the perspective of water vapor flux.The results show that the water vapor transport from northeast China,which usually occurs in late autumn and winter,can not bring much precipitation to South China.However,during the flooding season,the main water vapor transport that brings sufficient precipitation to South China is from the South China sea flow and southwesterly flow related to the Indian summer monsoon.