ALBERT

Description: A meta-analysis data-driven approach is developed to represent the soil evaporative efficiency (SEE) defined as the ratio of actual to potential soil evaporation. The new model is tested across a bare soil database composed of more than 30 sites around the world, a clay fraction range of 0.02-0.56, a sand fraction range of 0.05-0.92, and about 30,000 acquisition times. SEE is modeled using a soil resistance ( r ss ) formulation based on surface soil moisture ( θ ) and two resistance parameters r ss,ref and θ efolding . The data-driven approach aims to express both parameters as a function of observable data including meteorological forcing, cut-off soil moisture value θ 1/2 at which SEE=0.5, and first derivative of SEE at θ 1/2 , named . An analytical relationship between ( r ss,ref ; θ efolding ) and ( θ 1/2 ; ) is first built by running a soil energy balance model for two extreme conditions with r ss = 0 and r ss ∼ ∞ using meteorological forcing solely, and by approaching the middle point from the two (wet and dry) references points. Two different methods are then investigated to estimate the pair ( θ 1/2 ; ) either from the time series of SEE and θ observations for a given site, or using the soil texture information for all sites. The first method is based on an algorithm specifically designed to accomodate for strongly nonlinear SEE( θ ) relationships and potentially large random deviations of observed SEE from the mean observed SEE( θ ). The second method parameterizes θ 1/2 as a multilinear regression of clay and sand percentages, and sets to a constant mean value for all sites. The new model significantly outperformed the evaporation modules of ISBA (Interaction Sol-Biosphére-Atmosphére), H-TESSEL (Hydrology-Tiled ECMWF Scheme for Surface Exchange over Land), and CLM (Community Land Model). It has potential for integration in various land-surface schemes, and real calibration capabilities using combined thermal and microwave remote sensing data. This article is protected by copyright. All rights reserved.