Using precipitation, vertical root distribution, and satellite‐retrieved vegetation information to parameterize water stress in a <scp>P</scp>enman‐<scp>M</scp>onteith approach to evapotranspiration modeling under <scp>M</scp>editerranean climate

Abstract

Abstract Recent studies have shown that global Penman‐Monteith equation based (PM‐based) models poorly simulate water stress when estimating evapotranspiration (ET) in areas having a Mediterranean climate (AMC). In this study, we propose a novel approach using precipitation, vertical root distribution (VRD), and satellite‐retrieved vegetation information to simulate water stress in a PM‐based model (RS‐WBPM) to address this issue. A multilayer water balance module is employed to simulate the soil water stress factor (SWSF) of multiple soil layers at different depths. The water stress factor (WSF) for surface evapotranspiration is determined by VRD information and SWSF in each layer. Additionally, four older PM‐based models (PMOV) are evaluated at 27 flux sites in AMC. Results show that PMOV fails to estimate the magnitude or capture the variation of ET in summer at most sites, whereas RS‐WBPM is successful. The daily ET resulting from RS‐WBPM incorporating recommended VI (NDVI for shrub and EVI for other biomes) agrees well with observations, with ( 18.72 ) for all 27 sites and ( 18.21 ) for 25 nonagricultural sites. However, combined results from the optimum older PM‐based models at specific sites show ( 20.74 ) for all 27 sites. RS‐WBPM is also found to outperform other ET models that also incorporate a soil water balance module. As all inputs of RS‐WBPM are globally available, the results from RS‐WBPM are encouraging and imply the potential of its implementation on a regional and global scale.