| In the background of global warming,drought has become one of the most destructive natural disasters in the world and has attracted widespread attention from all walks of life.The Inner Mongolia Autonomous Region(IMAR),as an important ecological barrier in China,is also a major grassland animal husbandry and agricultural region in China.It has been severely affected by drought and frequent regional droughts,which have brought serious negative impacts on people's lives and agricultural.Therefore,studying the spatial-temporal evolution characteristics,development trends,and drought response issues of the region has important scientific significance for drought relief efforts and regional agriculture and animal husbandry of local government.In this paper,the standardized precipitation evapotranspiration index(SPEI)is used as a meteorological drought monitoring index,and the long-term serial drought change trend in IMAR from 1970 to 2018 is discussed.The temperature and vegetation drought index(TVDI)is used as the ecological drought monitoring index to reconstruct the temporal and spatial information of drought during the drought intensification period(2000-2017)in the meteorological drought monitoring results,and quantitatively monitored the spatial distribution pattern of drought in IMAR in the past 18 years with a view to further accurately monitor the changing characteristics and trends of integrated drought in IMAR.On this basis,the trend analysis method and correlation analysis method are used to study the relationship between drought evolution trends and drought response to climate factors.The main conclusions reached are as follows:(1)From 1970 to 2018,the annual average air temperature is 4.47°C,and the annual average air temperature rises significantly at a rate of 0.4°C/10a in 49 years in IMAR.From 1989 to 1996,it is the key period that causes the air temperature change,and winter warming lasts the longest.The annual average precipitation from1970 to 2018 is 334.11mm in IMAR,of which 1998 is the time point when the precipitation suddenly changes.From the seasonal variation of precipitation,the short-term change in precipitation is obvious,and the precipitation is mainly controlled by the precipitation in summer in IMAR.(2)From 1970 to 2018,the region of IMAR shows aridity under SPEI monitoring at different time scales.After 2000,the drought intensity has been significantly strengthened,compared with SPEI at different time scales.It is found that SPEI-3 can better monitor seasonal drought in IMAR.According to the changes of SPEI-3,drought conditions in spring,summer and autumn have all intensified since the beginning of the 21st century.Various analyses indicate that droughts that occurred after 2000 lasted longer and occurred more frequently.(3)In terms of SPEI drought frequency,the site with the highest frequency of mild droughts is Siziwangqi,the highest frequency of moderate droughts is Kailu,the highest frequency of severe droughts is Aershan,and the frequency of extreme droughts is Gilan.Thai.From 1970 to 2018,the proportion of drought-stricken sites increased sharply with a trend of 9.3/10a(r=0.51)in IMAR.A total of 11 years reaches full coverage drought,12 years are regional drought,and 13 years are localized drought,there is almost no drought in 13 years.Among them,2000,2001,2007 and 2017 are the four years with the largest drought coverage in 49 years.(4)The average value of TVDI in the growing season from 2000 to 2017 is0.6,and the area of heavy drought and moderate drought is the largest,of which 2007and 2010 are the years with the most severe drought in IMAR.The spatial differentiation of drought is obvious in IMAR.The moderate drought slightly occurs in the area of southwest,and mainly in the middle part,in addition,Hulunber grassland in the west of Daxing'an Mountainsis severely affected.In the past 18 years,the drought degree shows a slight increase trend,and the interannual variation?sloperanged from-0.07 to 0.7 in IMAR.The drought trend is most obvious in the area from the northeast of Alukorqin Banner to the Huolin River.The drought situation in Arong Banner,Zhalantun and other agricultural production banners has a slight increase.During the growing season of 2017,drought was the most serious in June and September,and drought occurred frequently and severely in Hulunber grassland and western Ordos Plateau in IMAR.(5)TVDI is positively correlated with the average air temperature,negatively correlated with the cumulative precipitation.The analysis of partial correlation between TVDI and climatic factors in growing season shows that the drought in Northern Sunite Left Banner of Xilingol League,Oroqen Autonomous Banner and Hulunber grassland has a significant positive correlation with air temperature(P<0.01),and the drought in northeastern Xilingol League has a significant negative correlation with precipitation(P<0.01),the average air temperature has a stronger impact on drought than cumulative precipitation. |
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