An application of the maximum entropy production principle in modeling heat fluxes over land surfaces

A model of evaporation, sensible and ground heat fluxes over land surfaces is proposed based on the theory of maximum entropy production (MEP). A key element of the proposed MEP model is the formulation of a dissipation (or entropy production) function, whose extremization under the constraint of conservation of energy leads to a unique partition of net radiation into latent, sensible and ground heat fluxes. The solutions are functions of surface soil temperature, surface specific humidity (or its equivalents such as soil wetness) and net radiation. The MEP model predicts that surface heat fluxes vary monotonically and smoothly with soil wetness ranging from dry to saturation. The MEP model of transpiration over vegetated surfaces is shown to be a special case of non-vegetated surfaces. A test of the MEP model using field observations indicates that the model performs well under all soil moisture conditions and no-water-stress canopy. The proposed MEP model is an effective tool in modeling the energy budget over a land surface due to its unique features: (1) the model is built on the state-of-the-art non-equilibrium thermodynamics, (2) the model only needs input of surface variables (i.e. temperature, humidity or its equivalents, and net radiation), (3) the model covers the entire range of water states from dryness to saturation, (4) all model parameters are either physical properties of the system or universal empirical coefficients, and (5) the model formulation allows a unique solution of the fluxes with reduced sensitivity to the uncertainties in the model parameters.