Decoupling vegetation and soil-moisture interaction in evapotranspiration interannual variability

Abstract

Evapotranspiration (ET) shapes climatic variability through the land-atmosphere coupling (LAC). While the relationship between soil moisture and ET is intuitive, the dynamical interaction among vegetation, soil moisture, and ET in LAC is understudied. Here we disentangle soil moisture and the vegetation influence on ET interannual variability using the Community Earth System Model. Globally, 55.7% of the land shows high soil moisture and vegetation coupling with ET. Soil moisture-ET coupling predominates in low-latitude LAC hotspots, while vegetation-ET coupling dominates in arid areas and high latitudes where shrubs and grasses prevail. In high-temperature and low-precipitation areas, soil evaporation induces an ET variability of 0.072 mm day−1, whereas transpiration exerts stronger variability of 0.092 mm day−1. The findings underscore the essentiality of vegetation in ET dynamics, suggesting that its influence may be underestimated in current LAC assessments—and that such underestimation could heighten the risk of extreme events in a warming climate. Graphical abstract: [Figure not available: see fulltext.]