Estimation of Sensible and Latent Heat Flux Over Mountainous Areas Using the SEBAL Model

Accurately estimating sensible heat (H) and latent heat (LE) in mountainous areas is a significant challenge due to the influence of complex topography factors. Currently, most models have been developed to estimate surface heat flux for flat surfaces without considering the effect of complex geometric terrain structures. In this study, the surface energy balance algorithm for land (SEBAL) coupled with a mountainous net surface radiation ( $R_{n}$ ) calculation method (MSEBAL) was proposed to accurately estimate H and LE in the upstream catchment regions of the Heihe River Basin (HRB). $R_{n}$ was estimated by correcting the solar incoming radiation components using topographic factors, including slope, aspect, sky view factor (SVF), and terrain configuration factor (TCF). The SEBAL and MSEBAL models were applied to satellite remote sensing (RS) data from Landsat 8 images and ground-observed datasets. In situ measurements from the eddy covariance (EC) system of the A’rou superstation were used to validate the estimation accuracy of $R_{n}$ , LE, and H by MSEBAL. The results show that $R_{n}$ , LE, and H estimated by the MSEBAL exhibit good consistency with the validation of in situ measurements. $R_{n}$ estimated by MSEBAL showed a decrease in RMSE from 164.32 to 51.31 W/m2 and a reduction in absolute bias from 154.50 to 10.50 W/m2 compared to SEBAL. The H and LE estimated by MSEBAL exhibit low RMSE and bias, with values of 31.96 and −17.93 W/m2 for H, and 35.67 and −6.18 W/m2 for LE, respectively, compared to SEBAL. The spatial pattern of surface heat fluxes exhibited variations with complex terrain changes. H and LE were found to be higher at mountain peaks, while lower values were observed in valleys. Additionally, H and LE were greater on east- and south-facing slopes that receive more solar radiation compared to west- and north-facing slopes. This study provides an effective tool for estimating surface heat fluxes over mountainous regions.