Impacts of Temporally Compounding Hot-Dry Events on Agricultural Droughts via Vegetation in the Yangtze River Basin

Abstract

Vegetation has an important impact on hydroclimatic conditions via its impacts on water, energy, and carbon exchanges of the terrestrial land surface. The vegetation greening of earlier spring can cause summer drying of soil moisture, reflecting the trans-seasonal lagged effects of the spring phenology. Meanwhile, the direct influence of meteorological droughts on agricultural drought has also been well recognized. However, the combined effects of antecedent vegetation conditions and subsequent meteorological droughts on agricultural droughts, particularly from a temporally compounding event perspective, remain insufficiently understood. In this study, we examined the characteristics and impact of temporally compounding hot-dry (TCHD) events on agricultural droughts through vegetation dynamics in the Yangtze River Basin (YZRB) from 2000 to 2022. Such events are observed in the YZRB during the three years 2013, 2018, and 2022. The normalized difference vegetation index (NDVI) for the three years during spring is 2.44%, 7.24%, and 9.65% higher than the multiyear average, accompanied by higher actual evaporation ( E ) during spring. Combined with the precipitation deficits during summer, the preseason vegetation was associated with cascading impacts on soil moisture, resulting in lower soil moisture levels ( − 3.06 % and − 4.76 % lower than the multiyear mean) for 2013 and 2022. Moreover, the soil moisture of the TCHD is lower than that under dry summer conditions only, implying the importance of spring vegetation greening in driving agricultural droughts during summer. Based on the multiple linear regression, the contribution from preseason vegetation to summer soil moisture deficits during 2022 is also quantified. Findings of the study can be useful for understanding the climate extreme-vegetation relationship under a greening Earth.