Temporal And Spatial Variation Characteristics Of Precipitation And Extreme Precipitation In Guangxi

Under the background of global warming,the study of spatiotemporal variation of precipitation and extreme precipitation has been a hot topic and a theoretical basis for further understanding of the causes of flood disaster.Based on the data of precipitation from 1971 to 2012,the trend and spatial distribution of annual,seasonal and daily precipitation are studied in different districts.The evolution of different duration precipitation are studied by the index of precipitation incidence and contribution rate.Secondly,this paper analyzes the relationship between precipitation and temperature in typical cities of Guangxi by the Copula function theory.Finally,the extreme precipitation in Guangxi is studied by using the index of severity index,aggregation degree and aggregation period.The main conclusion is as follows:(1)The annual precipitation in Guangxi is increasing from the Midwest to the northeast and the south.The trend of precipitation in southeast region is declined,while the precipitation of coastal region is increased.The precipitation in northwest has a main wet season in 1991?2002,while there were two main wet seasons in 1977?1986,1995?2004 in the others.The spatial distribution of precipitation is rainy(rainless)and southern-rainy and northern-dry(southern-dry and northern-rainy).The daily precipitation distribution asymmetry degree showed a trend of increase,reflecting the extreme precipitation intensity increases the possibility of most area.(2)The incidence and contribution rates of precipitation in short duration are declined,while it's rise in long duration.But the rates of precipitation in moderate duration is different in the area of change.And the distribution of high and low frequency period of incidence and contribution rates of precipitation in 1?3h,4?6h,7?12h of Guangxi were consistent.The frequency period of the rates in 12h are inconsistent in different area.(3)There are some differences between the correlations of precipitation and air temperature in different seasons and different districts.It can be characterized by Frank Copula function in the autumn of Guilin,summer of Nanning,summer and winter of Beihai.And the construction of the correlation is different in the year.It can be characterized by normal Copula function in Guilin,while it's characterized by Frank Copula function in Nanning and Beihai.(4)The frequency of the extreme precipitation events in northeastern and eastern regions parts are higher,while the average intensity and severity index of extreme precipitation in coastal areas and northeastern regions are relatively large,which indicates that these areas prone to floods.The frequency and intensity are increasing in most area except for coastal region.The extreme precipitation events occurred from June to August more likely,and the occurrence time in northwest and coastal areas is relatively concentrated.The happened time and concentration of extreme precipitation events had different change in different times.