Contrasting Evaporative Responses of Ecosystems to Heatwaves Traced to the Opposing Roles of Vapor Pressure Deficit and Surface Resistance

Abstract

AbstractUnderstanding the evaporative response of ecosystems to heatwaves is critical for managing ecosystem services and water resources, especially under a changing climate. In this study, we examine the land‐atmosphere exchange of water and heat fluxes under heatwave and nonheatwave conditions across five different land cover types, including grasslands, shrublands, croplands, deciduous broadleaf forests, and evergreen needleleaf forests, using data from eddy covariance towers. Results show that net radiation and sensible heat flux increase from nonheatwave to heatwave conditions across all five land cover types but latent heat flux shows contrasting responses to heatwaves. An attribution analysis further demonstrates that heatwave‐induced changes in evaporative fraction are mainly caused by changes in vapor pressure deficit (positive contribution) and changes in surface resistance (negative contribution). The imbalance between the positive and negative contributions varies across the five land cover types and is responsible for their contrasting evaporative responses to heatwaves.