Evolution And Prediction Of Dry Spatial And Temporal Conditions In Yunnan Province Under Climate Change

Global warming is making climate change a hot-button environmental issue today,which attracted widespread attention from governments,researchers,and people around the world.Frequent drought events caused by climate change have induced impacts on human life and industrial and agricultural production and become an important aspect of their impact.As one of the countries with frequent droughts,China is experiencing the droughts with high frequency,prolonged duration,wide impact and heavy losses under climate change.Yunnan Province is a province of southwestern China,and it is a major crop production province and sensitive to climate change.Studying the climate change characteristics in the historical period of the region and predicting the climate change tendency in the future scenario is extremely important for the analysis of the evolution of drought disasters.Taking Yunnan Province as study area,meteorological drought as study object,standardized precipitation index(SPEI)as main monitoring indicator,this study analyzed the temporal and spatial characteristics of temperature and precipitation and their drought trends,as well as temporal and spatial evolution characteristics of related drought assessment indicators in Yunnan Province from 1961-2018 based on historical period meteorological data from different climate scenarios.Furthermore,it also explored the impact of atmospheric circulation on drought in Yunnan Province and predicted the future temporal and spatial changes of drought under the shared socio-economic pathway(SSP126,SSP245,SSP370,and SSP585)scenario of the International Coupled Model Comparison Program(CMIP6).The main conclusions are as follows:(1)On an interdecadal scale,the average temperature in Yunnan Province has been warming continuously since the 1960 s.At the same time,the temperature of Yunnan Province has been increasing continuously in all four seasons,with the warming rate of the four seasons ranked as summer > autumn > winter > spring,and a greater influence of summer and winter on the climate warming in Yunnan Province.Spatially,there was a decreasing trend in the north-south direction and a relatively obvious warming in the middle.While from the east-west direction,the warming rate was high in the middle and low in the two ends,and the temperature increase or decrease distribution had a clear regional nature.Annual precipitation in Yunnan decreased at a rate of-5.21 mm/10 a and overall precipitation was low after 2000,indicating the aridity tends to be severe.The rate of change was sorted from large to small as summer > spring > fall > winter.Spatially,precipitation in Yunnan Province showed an increasing trend mainly in the northern,northeastern and partly southern regions,and a decreasing trend mainly in the eastern,western and central regions.In addition,precipitation mainly increased in winter and spring,decreased in summer and autumn,and greatest decreased in summer.(2)The drought in Yunnan Province underwent an abrupt change from wetter to drier in 1994,and the drought in west-east direction was more severe in the west and milder in the east,and the drought in the west was still increasing.The four-season drought in Yunnan Province tended to become more severe after 2000,among them,summer drought being the most pronounced.Spatially,the winter drought trend was greatest in the western part of the study area,followed by summer and autumn,with summer drought mainly concentrated in the central and western regions and autumn drought mainly in the northeast.Droughts occurred more frequently in the western and northern parts of Yunnan and part of the south,with the overall frequency varying from mild to moderate drought > medium drought > severe drought > extreme drought.At the interannual scale,Yunnan Province was predominantly lightly droughty,and other degrees of drought occurred at different frequencies.From the spatial distribution of seasonal drought frequency,winter > autumn > spring > summer,drought occurred very frequently in Yunnan province in spring and above medium winter.In addition,the drought in Yunnan Province was mainly influenced by the El Ni?o-Southern Oscillation(ENSO)and East Asian Summer Wind Index(EASMI)index changes.(3)Under different scenarios,the average annual temperature in Yunnan Province increased gradually over time.The warming in autumn was very pronounced,and the overall warming in winter was the smallest compared to other seasons,except for a pronounced warming in the SSP370 scenario.Compared to the historical period 1961-2018,the trend of future warming will generally increase,and the phenomenon of warm spring and warm autumn will increase.In addition,the warming trend was also generally increasing in spatial.With the increased socio-economic concentration of the sharing,the precipitation had a significant change in space that the decreasing trend was increasing,and the precipitation in most areas of Yunnan Province was decreasing under different scenarios,which will lead to growing drought.(4)As the shared socioeconomic concentration increases,the standardized precipitation evapotranspiration index(SPEI)decreased in the Yunnan region from 2019 to 2040.It significant decreased at rates of-0.639/10 a and-0.764/10 a in the SSP245 and SSP585 scenarios,and the change trend in the SSP370 scenario being closest to the historical period.Spatially,its decreasing trend was gradually increasing from the eastern to the western part of the study area.At the same time,as the concentration of the shared socio-economic path increases,the value range of drought frequency in Yunnan Province was gradually decreasing,in which the SSP245 and SSP370 scenarios are close to the historical trend of drought changes and drought occurrence range,and in the future,Yunnan Province was likely to have severe drought disasters.