Impacts of soil heat flux calculation methods on the surface energy balance closure

Quantifying uncertainty in determining the surface soil heat fluxes (G0) to close the surface energy balance in micrometeorological studies remains an open question. While numerous methods have been proposed to determine G0 and have been validated individually, few studies have cross-evaluated these methods to examine how the derived G0 from different methods affects the closure of the surface energy balance. Using data measured at an arid shrub-land site during summertime, nine different methods were evaluated ranging from conventional heat-storage calorimetry to methods derived directly from the heat transfer equation. Apart from the entire dataset, two subsets were used; one with minimal variation from idealized diurnal radiation cycles and the other with highly variable radiation conditions. Under the entire dataset, the performance of the methods varied while there was a distinct drop-off in the level of closure under the variable radiation conditions. The methods that allowed for the most variation in inputs between time steps performed better than those that used diurnal or constant input values. Because of this, a calorimetry method and Green's function-based method are more highly recommended than other methods.