Summer atmospheric drying could contribute more to soil moisture change than spring vegetation greening

Abstract

Widespread spring vegetation greening (inferred by LAI) in the Northern Hemisphere leads to additional summer soil moisture (SM) deficits through increasing transpiration. Meanwhile, vapor pressure deficit (VPD) has also been rising, which can increase atmospheric evaporative demand. However, the extent and magnitude of influence of these two factors on SM changes have not been elucidated. Here, based on the state-of-the-art reanalysis and remote sensing data, we use three statistical methods to quantify the contributions of spring LAI and summer VPD to summer SM deficit. The results show that summer VPD contributes more to SM change than spring LAI in the southwestern and northern regions of North America, northeastern Europe, and central and southeastern Asia, covering 13.4% of the vegetated areas despite of the certain influence of spring vegetation greening on summer soil drying. The results are of great significance for climate change adaptation and the enhancement of surface water management.