Evaluation of soil resistance formulations for estimates of sensible heat flux in a desert vineyard

For irrigated vineyards, accurate estimates of the sensible heat flux from the soil surface (Hs) is essential for determining the contribution of soil evaporation (E) to evapotranspiration (ET) using thermal-based energy balance approaches. A key to an accurate estimate of Hs is a robust physically-based soil resistance formulation. Here we compare the performance of two soil resistance formulations: a conventional resistance model (rKN) derived from field and laboratory studies which has been extensively implemented in the thermal-based Two-Source Energy Balance (TSEB) model, and a recently developed physically-based soil resistance formulation (rHO) that explicitly accounts for near-surface interactions affecting scalar fluxes at the soil surface in the presence of bluff-body roughness elements. Estimates of Hs using the two resistance formulations were evaluated using in-situ observations from a drip-irrigated vineyard in the arid central Negev Highlands of Israel. The results indicate that the soil resistance model rHO outperforms the rKN formulation using standard model coefficients and provides robust estimates of Hs independent of model calibration or parameter tuning. This offers an opportunity to advance the utility of TSEB model when applied to sparsely vegetated areas where ground-based calibration data are not available for adjusting coefficients in the rKN formulation, and potentially improves its practical applications to heterogeneous landscapes by obviating its reliance on semi-empirical coefficients.