Spatial and temporal variations of drought in Sichuan Province from 2001 to 2020 based on modified temperature vegetation dryness index (TVDI)

Investigating the drought response to evapotranspiration and climate change was key to understanding the dynamics of drought changes and the mechanism of drought changes in the future. In this study, a modified Temperature Vegetation Drought Index was constructed based on the correction of elevation and incorporating air temperature and also based on climate indices recommended by the Expert Team on Climate Change Detection and Indices (ETCCDI) the effects of evaporation and vegetation cover on the drought in Sichuan Province were investigated. The results showed that: the degree of drought in the northwestern Sichuan Plateau (0.57 < TVDI < 0.86) was weaker than in other regions (the Chengdu Plain, the Eastern Sichuan Basin Plain, and southwestern Sichuan's mountainous region) with TVDI < 0.86. Agricultural land and construction land had a relatively high degree of drought (0.76 < TVDI < 0.86), the decreasing trend was insignificant in the whole province. The drought degree in spring was the least, and the main trend was insignificant; 0-0.01/a in summer. The drought in autumn and winter was more severe, and most areas of the province were extremely dry, showing an increasing trend. The minimum and maximum value of ET was concentrated in the northwestern Sichuan Plateau (ET < 130 mm) and the Sichuan Basin (ET < 170 mm), respectively. ET of water bodies (ET >= 170 mm) was the highest, and lowest in construction land (90 < ET < 130 mm). The increase rate of ET was highest in spring and lowest in winter. TVDI was negatively correlated with annual precipitation in the northwestern Sichuan Plateau, Jinsha River Valley, and eastern Chengdu Plain, positively correlated with annual temperature and positively correlated with the yearly minimum value of daily minimum temperature (TNn), the yearly minimum value of daily maximum temperature (TXn), and the yearly maximum value of daily minimum temperature (TNx), and negatively correlated with the yearly maximum value of daily maximum temperature (TXx) and the yearly maximum consecutive five-day precipitation (PX5). The results are useful for the understanding of drought and policy making of climate change.