Spatial-temporal Analysis Of Drought In Southwest China Based On No Effective Precipitation Index

Under the background of global warming,drought disasters have become more serious,drought frequency and intensity have increased,and direct and indirect economic losses have continued to increase.This has had a profound impact on social stability and economic development.In recent years,with the rapid development of the national economy,population growth and the acceleration of urban development,drought disasters are developing from the agricultural field and rural areas to the secondary industry,tertiary industry and urban areas.Southwest China is an important mineral and agricultural base in my country.Therefore,it is of great practical significance to carry out drought research in Southwest China.Therefore,this paper selects the southwest region as the research area to explore the temporal and spatial variation of its drought.Based on the daily precipitation data of 117 stations from 1960 to 2016(57a)in the five provinces,autonomous regions and municipalities(Guangxi,Yunnan,Guizhou,Sichuan and Chongqing),this paper selects the index of no effective precipitation days to establish a time series of annual and seasonal no effective precipitation days(LCDD).Inverse distance weighted interpolation(IDW),Mann-Kendall trend analysis,linear trend statistical analysis and other methods are used to analyze the spatial and temporal evolution of the annual and seasonal no effective precipitation days and the longest continuous no effective precipitation days,and according to the number of no effective precipitation days The data calculates the frequency of annual and seasonal droughts and the comprehensive intensity of the drought,and finally summarizes the spatial and temporal characteristics and influencing factors of drought in the southwest region.The main results of the research are as follows:(1)The years of non-effective precipitation days in the southwestern region fluctuate and increase in time,showing the law of "more west and less east" in space.Among them,Yunnan and Sichuan have the largest number of non-effective precipitation days and have a trend of increasing year by year.,And the trend change passed the 95% significance test.The days with no effective precipitation in Yunnan and Sichuan are concentrated in spring and winter,the days with no effective precipitation in Guizhou and Chongqing are concentrated in summer,and the days with no effective precipitation in Guangxi are concentrated in autumn.The trend of the longest continuous no effective precipitation days is relatively stable.Among them,the longest continuous no effective precipitation days in Sichuan are more and showing a downward trend,and pass the 95% significance test.The longest consecutive days without effective precipitation in spring and winter are the most,and the longest consecutive days without effective precipitation in autumn are the most obvious.(2)Drought may occur in any season in the southwest region,but it is mainly concentrated in the spring and winter seasons.Except for the frequency of spring droughts,there was no obvious trend,and the frequency of droughts in the remaining three seasons all showed an increasing trend and passed the 95% significance test.Among provinces,autonomous regions and municipalities,Yunnan and southwestern Sichuan have the most frequent spring and winter droughts,Chongqing and Guizhou have the most frequent summer droughts,and Guangxi has the most frequent autumn droughts.(3)The comprehensive intensity of drought in all seasons in the Southwest shows an upward trend.The highest annual average comprehensive intensity of drought in southwestern regions is mainly concentrated in Yunnan and southwestern Sichuan,and the overall spatial distribution pattern is "high in four weeks and low in middle".The eastern and southern parts of Yunnan and Sichuan have the highest comprehensive drought intensity in spring;Chongqing,Guizhou,northwestern Guangxi and eastern Sichuan have the highest comprehensive summer drought intensity;Guangxi has the highest comprehensive autumn drought intensity;Yunnan and most parts of Sichuan have the highest winter drought comprehensive intensity.