Temporal And Spatial Evolution And Prediction Of Meteorological Drought In The Poyang Lake Basin Under Climate Change

Drought is one of the most devastating natural disasters in the world and an important aspect of the many effects of climate change.In the context of climate change,the wide-ranging and frequent drought has brought many adverse effects on human production,life and economic and social development.The Poyang Lake Basin is one of the rainy areas in China,and the seasonal and interannual variations of precipitation are relatively large.With the global climate change,drought events occur more frequently,and the degree of drought in the basin is increasing.Therefore,the study of climate history in the region and the prediction of different climate change scenarios in the future have important scientific significance for analyzing the evolution of meteorological drought disasters in the basin.This study takes meteorological drought in Poyang Lake Basin as the research object,and analyzes the applicability of standardized precipitation evapotranspiration index(SPEI)and standardized precipitation index(SPI)in Poyang Lake Basin,based on meteorological data,climate model data,atmospheric circulation data and land use.The data were analyzed for the temporal and spatial variation of temperature and precipitation in the Poyang Lake Basin from 1961 to 2018.The interannual and four seasons drought indices,drought frequency,drought station times and drought intensity temporal and spatial characteristics were analyzed,and the drought and Poyang Lake Basin agriculture were analyzed.The relationship between production and the causes of drought in the Poyang Lake Basin;the main changes in the droughts from 2019 to 2100 under the RCP2.6,RCP4.5 and RCP8.5emission scenarios are as follows:(1)The annual average temperature of the Poyang Lake Basin showed a significant upward trend at a rate of 0.22°C/10a,and the temperature increase was the fastest from1980s to 1990s.The temperature in the four seasons showed a trend of warming,and the rate of warming was spring>winter>autumn>summer.The annual precipitation in the basin shows an increasing trend at a rate of 30.44mm/10a,with strong volatility and uneven distribution of annual precipitation,showing a change of“increasing-decreasing-increasing”.The variation rate of precipitation in the four seasons is summer>autumn>winter>spring.By analyzing the SPI and SPEI indices,the short,medium and long-term droughts in the Poyang Lake basin are compared with the statistics of the Chinese meteorological disasters.The drought status and actual average of SPEI are compared.The anastomotic rate is 71.58%,which can accurately characterize the interannual and seasonal variations,spatial and temporal distribution,and drought index assessment of meteorological drought in Poyang Lake Basin.(2)In the past 58 years,the annual SPEI of the Poyang Lake Basin increased at a rate of 0.03/10a.In the past ten years,the drought and humidification alternated,and the fluctuation was large.Only the spring drought index in the four seasons showed a decreasing trend.The average drought frequency in the basin is 34.08%.With the increase of drought level,the frequency of drought decreases.The average frequency of drought in the four seasons is 32.76%,33.16%,34.35%and 29.71%,respectively.The annual and seasonal droughts are all light and drought.Mainly in the middle and drought,the annual drought frequency shows the distribution characteristics of“south high and low north”.In terms of the four seasons,the drought mainly occurs in the northeast and southwest of the basin.The ratio of drought stations in the basin over the years is between 0%and 100%,with an increasing trend of 0.33%/10a.The years of the five types of drought are 23a,11a,0a,6a,18a,mainly with global drought and local area.Sexual drought is dominant.The ratios of drought stations in spring and autumn,summer and winter showed an increase and decrease trend respectively.In the interdecadal,the annual scale and spring have the largest impact on the 2000S drought,while the summer,autumn and winter have the greatest impacts in the1980S,1970S and 1960S droughts.The drought intensity of the basin for many years was0.71,and the annual drought intensity increased by 0.02/10a.There was no drought in 15years,the drought intensity was between 0.54 and 1.90,and the drought intensity was the highest in 1998,1.90.The average annual drought intensities in the four seasons of the Poyang Lake Basin were 0.68,0.83,0.68 and 0.59,respectively.It is the largest in summer,followed by spring and autumn,and lowest in winter.In the interdecadal,the 1960S and2000S droughts were more serious,and the 1980S was lighter.The correlation coefficient between the SPEI12 index of the Poyang Lake Basin and the affected area,disaster area and unacceptable area caused by drought reached the maximum in April,which were-0.671,-0.654 and-0.611,respectively,and stabilized after May.The SPEI12 index can well reflect the changes in the arid area of the Poyang Lake Basin.(3)The annual average and seasonal temperature of the Poyang Lake Basin are characterized by the continuous increase of greenhouse gas emission concentration,and the greater the concentration of greenhouse gases,the greater the increase in temperature;the future temperatures of the four seasons exist under various scenarios.Temperature increase,the summer temperature in the RCP8.5 scenario increased by 5.62°C,followed by spring,autumn and winter.The annual precipitation also increases with time,that is,in the early21st century,the mid-term<end period,the four seasons precipitation is the largest under the RCP4.5 emission scenario,the RCP8.5 is the second,and the RCP2.6 is the smallest.The increase of precipitation in the four seasons is from spring to summer>summer>winter>autumn.With the increase of greenhouse gas emission concentration,the SPEI of the drought index in the Poyang Lake Basin increased from 2019 to 2100,RCP4.5 and RCP8.5The rate of-0.099/10a and-0.329/10a decreases significantly;in space,the decreasing trend gradually increases from the northeast to the southwest of the study area.The annual scale drought in the Poyang Lake Basin under the three emission scenarios is dominated by mild drought and moderate drought.With the increase of drought grade,the frequency of drought is smaller.The four seasons of drought under the three emission scenarios mainly occurred in the middle and late 21st century.With the increase of greenhouse gas emission concentration,the drought intensity and drought intensity in the Poyang Lake Basin increased from 2019 to 2100.(4)From the perspective of geographical environment,the Poyang Lake basin is located in the middle and lower reaches of the Yangtze River in the mid-latitude region.The precipitation is unevenly distributed in time and space.The precipitation has significant seasonality and regionality,and the interannual variation is large,which leads to the drought in the Poyang Lake Basin.Phenomena occur frequently.From the perspective of atmospheric circulation factors,the Arctic Oscillation(AO)and the East Asian Summer Monsoon Index(EASM)have higher correlations with the SPEI index and have a greater impact on the drought in the Poyang Lake Basin.There was a significant negative and positive correlation between SPEI and NAO and PDO index,and the correlation between AO index and EASM index and SPEI was positively correlated in the southwest,northeast and central parts of Poyang Lake Basin.AO and SPEI have resonance periods of 4a,7km~29a,17a and 1km~23a in four periods.From the time,intensity and occurrence time of the ENSO warm and cold events from 1961 to 2018 and the SPEI average of the Poyang Lake Basin,it is concluded that the Poyang Lake Basin is more prone to drought when a warm event(El Ni?o event)occurs.From the perspective of human activities,from 1980 to 2015,the area of construction land for residents in Poyang Lake Basin increased the most,reaching 2241.01kmkm~22,and the area of cultivated land decreased the most,which was 1227.96kmkm~22,which was mainly converted into forest land and water body,and the area of forest land reduction was second.It is 1010.45kmkm~22 and is mainly converted into cultivated land and grassland.The forest land and grassland have decreased in the Poyang Lake Basin in the past 35 years,providing conditions for the occurrence of drought events.