Abstract
Wind speed (u) is a significant constraint in the evapotranspiration modeling over the highly heterogeneous regional surface due to its high temporal-spatial variation. In this study, a satellite-based Wind Speed Avoiding Priestley–Taylor (WAPT) algorithm was proposed to estimate the regional actual evapotranspiration by employing a u-independent theoretical trapezoidal space to determine the pixel Priestley–Taylor (PT) parameter Φ. The WAPT model was comprehensively evaluated with hydro-meteorological observations in the arid Heihe River Basin in northwestern China. The results show that the WAPT model can provide reliable latent heat flux estimations with the root-mean-square error (RMSE) of 46.0 W/m2 across 2013–2018 for 5 long-term observation stations and the RMSE of 49.6 W/m2 in the growing season in 2012 for 21 stations with intensive observations. The estimation by WAPT has a higher precision in the vegetation growing season than in the non-growing season. The estimation by WAPT has a closer agreement with the ground observations for vegetation-covered surfaces (e.g., corn and wetland) than that for dry sites (e.g., Gobi, desert, and desert steppe).
Highlights
Terrestrial latent heat flux (LE) is an important component of the land surface water cycle and land surface–atmosphere energy exchange [1–4]
Many remote sensing models have been proposed to simulate terrestrial LE based on constraints on water vapor transport and energy balance constraints [2–4,7], such as SEBAL [8], SEBS [9], METRIC [10], TSEB model [11], Gc-TSEB [12], MOD16 [2], feature space methods [13–17]
The feature space to estimate LE was introduced by Jiang et al [21,22] with the scatter diagram of TL and vegetation index containing a full range of soil water content and fractional vegetation cover to linear fitting the triangle space with the advantages of no auxiliary atmospheric or ground data
Summary
Terrestrial latent heat flux (LE) is an important component of the land surface water cycle and land surface–atmosphere energy exchange [1–4]. Many remote sensing models have been proposed to simulate terrestrial LE based on constraints on water vapor transport and energy balance constraints [2–4,7], such as SEBAL [8], SEBS [9], METRIC [10], TSEB model [11], Gc-TSEB [12], MOD16 [2], feature space methods [13–17]. Those models have been proven successful for certain weather conditions, underlying surfaces, etc. The feature space model, which employs the triangle or trapezoidal relationship between land surface temperature (TL ) and vegetation index (VI) to represent the constraints of soil available water on LE, is widely accepted.
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