A physical scheme for estimating land surface energy partitioning: all information embedded in a single point soil measurement

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Wednesday, 7 January 2015
Zhi-Hua Wang, Arizona State University, Tempe, AZ; and J. Yang

The partitioning of solar energy into dissipative fluxes and heat storage over the land surface regulates atmospheric dynamics and thermodynamics via land-atmosphere interactions. While surface energy fluxes play a crucial role in meteorology and ecohydrology, their in-situ measurements are limited and sparsely distributed, and numerical parameterization remain a viable way of estimating the surface energy balance in many studies. Land surface temperature is a key parameter in numerical estimates, for it dictates the physics in the soil-land-atmosphere continuum and contains the signature of the surface energy balance. In this study, we developed a novel approach that reconstructs turbulent and ground heat fluxes at the land surface, based on a single depth soil measurement (temperature and moisture), provided the net radiation received at the surface is known. This method is based on the recent research advances in two separate fields, viz. the linear stability analysis for sensible and latent heat portioning, and the soil thermal analysis for ground heat flux estimates, both reducible to single variable functions of soil temperature. This approach provide a physically-based scheme for land surface energy estimates, as compared to another widely used method based on the Maximum Entropy Production (MEP) principle; the latter resorts to the generic information entropy and its applicability in linear thermodynamic systems remains debatable (e.g. in nocturnal and stable boundary layers). The proposed method is validated against field measurements of surface energy budgets for different landuse landcover types in different climatic zones, with good accuracy and numerical robustness. The study provides insight into how surface energy partitioning can be retrieved from implicit signature in the subsurface filed.