Spatial And Temporal Distribution Of Vegetation Drought And Its Lag To Meteorological Factors In Ziya River Basin

With global warming and frequent extreme drought events,drought has become a challenge for all mankind.China is located in the East Asian monsoon region,the frequency of extreme drought is increasing year by year,which seriously restricts the development of agricultural economy and national food security.Ziya River Basin is an important grain producing area in the north area of China.Therefore,it is of great practical significance to explore the lag effect of temperature and precipitation on vegetation and the spatial and temporal distribution of drought in Ziya River Basin for the construction of ecological environment,scientific and reasonable allocation of water resources and drought prevention.Taking Ziya River Basin as the research object,based on the meteorological station data and MODIS data from 2000 to 2015,this thesis explores the impact of meteorological factors on vegetation,and uses SPEI(standardized precision evolution index),SPI(standardized precision index),VCI(vegetation condition index)to analyze the impact of meteorological factors on vegetation,The spatial and temporal distribution of drought and the response of remote sensing drought index to multi time scale meteorological drought index in Ziya watershed were analyzed by VCI(1)From 2000 to 2015,the interannual temperature,precipitation and NDVI(normalized difference vegetation index)of Ziya River Basin showed an upward trend,and the vegetation growth in the basin was improved.Temperature,precipitation and NDVI change significantly in four seasons.(2)From 2000 to 2015,the proportion of negative correlation between temperature,precipitation and NDVI is high in Ziya River Basin.By introducing Armand lag algorithm,the correlation between temperature,precipitation and NDVI is improved.The lag effect of temperature and precipitation on vegetation can reach 9 months,and the influence of temperature and precipitation on vegetation is the largest in 0-3 months.(3)The variation trend of meteorological drought index SPEI and SPI from 2000 to2015 was the same.SPEI and SPI showed an increasing trend in interannual,spring and autumn seasons,and a decreasing trend in summer and winter seasons.The Ziya River Basin is dominated by light and medium drought,and the frequency of extreme drought is low.The remote sensing drought index VCI showed an increasing trend from 2000 to2015.The basin was mainly dominated by medium drought,and the occurrence and proportion of extreme drought were relatively low.(4)VCI had different responses to SPEI and SPI at different time scales in different seasons.The correlation between VCI index and January scale SPEI and SPI was high in summer,and the correlation between VCI index and March scale SPEI and SPI was high in spring,autumn and winter due to the hystering effect of meteorological factors on vegetation.