An Optimized Temperature-Vegetation-Precipitation Dryness Index And Its Application

Global drought risk is increasing and several countries are already active to intervene and prevent it.As one of the most destructive meteorological hazards,scientific monitoring and forecasting of aridity can not only improve the defense capability,but also support the rational layout of agricultural production to avoid risks.In this context,this study,the Enhanced Vegetation Index（EVI）,Land Surface Temperature（LST）and Precipitation（P）were used as new data sources based on the spatial distance model to construct an optimized multi-source remote sensing dryness index named Temperature-Vegetation-Precipitation Dryness Index（TVPDI_n）based on the spatial characteristics of the large-scale dryness and wetness temporal characteristics and the shortcomings of the TVPDI_origin（TVPDI_o）data source.The TVPDI_n of the long time series was also compared and analyzed with the classical drought index-Standardized Precipitation Evapotranspiration Index（SPEI-3）on a 3-month scale,different drought response level products of Solar-Induced Chlorophyll Fluorescence（SIF）,soil moisture（SM）from ESA CCI（European Space Agency’s Climate Change Initiative）,and total crop yield,then the sensitivity and validity of the TVPDI_n for wetness and dryness monitoring were synthesized and validated.On this basis,the dryness and wetness conditions and spatial distribution characteristics of Chinese territory from 2001 to 2021 were monitored,and the following conclusions were drawn:（1）Compared with the original data source TVPDI_o using the new multi-source remote sensing data source of precipitation and vegetation index to construct TVPDI_n,the overall correlation between the two and SPEI-3 was good,with a maximum of 0.57and 0.56,respectively（p<0.1）,but the overall TVPDI_n constructed in this study had a better fit compared to the original data source TVPDI_o and was more sensitive to the monitoring of dry and wet conditions.（2）According to the comparison of TVPDI_n with ESA CCI SM,TVPDI_n showed a high correlation of more than 0.9 with soil water content,which proved that TVPDI_n was highly consistent with soil moisture;compared with SIF,54.5%of the regional correlation coefficients were greater than 0.8（p<0.01）,and spatially,the correlation results were better in the northwest than in the east,indicating that the response of TVPDI_n to vegetation productivity is more agile in regions with continental climate such as the northwest.The results of correlation with grain yield comparison showed that good positive correlations were presented with TVPDI_n in Liaodong Peninsula,northern North China Plain,and most of Qilian Mountains,southern edge of Qinling Mountains,middle and lower reaches of Yangtze River,and South China,indicating that TVPDI_n has a high consistency in the changes of agricultural grain production in the above mentioned regions,and also proving the index in monitoring agricultural aridity and guiding agricultural production The good performance of the index in monitoring agricultural aridity and guiding agricultural production.（3）Applying the normalized TVPDI_n（NTVPDI_n）time series to analyze the terrestrial aridity environment in China,we found that the driest and wettest years in China in the last 20 years were 2001 and 2016,and the frequent dry and wet months were March and August.Spatially,the deserts and basins in the northwestern interior are dry all year round,the eastern dry and wet fluctuations are frequent,and the basins and plateaus along the Yangtze River,as well as the plains,have a weaker ability to regulate the terrestrial arid environment.Along the Inner Mongolia Plateau,Baiyu Mountain,Qilian Mountain to Bayan Kara Mountain,Hoh Xili Mountain,Tanggula Mountain and Gangdise Mountain,showing the dry and wet dividing line of China’s terrestrial arid environment in the past 20 years.Through the analysis of spatial and temporal data,the extreme aridity events in the past 20 years mainly occurred in the Kumtag Desert in the Tarim Basin and the Sandy Mountains in Shanshan,Xinjiang,as well as the Batangilin Desert in the Inner Mongolia Plateau,and the migration trajectories of the aridity events in the above mentioned areas were to the non-desert zone from"northeast","west"and"south",respectively.