Inverse modeling of coupled soil heat and moisture transport constrained by eddy covariance observations

Coupled soil–atmosphere heat and moisture transport is strongly influenced by phase change and water vapor dynamics. Evaporation and condensation form a crucial link between the soil water balance and the surface energy balance by coupling hydrologic and thermal processes through latent heat exchange. Accurate representation of these processes is therefore essential for modeling moisture and energy dynamics in variably saturated soil. In this study, an established physics-based model describing liquid water flow, water vapor transport, heat transfer, and the surface energy balance was calibrated using observations from an eddy covariance monitoring station. The model explicitly incorporates the surface energy balance and computes its individual components using a combination of physically based formulations and empirical parameterizations, making it particularly suitable for direct comparison with eddy covariance observations. Soil hydraulic and thermal properties, together with key surface energy balance parameters, including surface resistance, atmospheric emissivity, and surface albedo, were estimated through inverse modeling without direct soil sampling. Model calibration was performed using an evolutionary optimization approach and resulted in good agreement between simulated and observed soil moisture, temperature, and turbulent energy fluxes. The calibrated model provides a physically consistent representation of the eddy covariance observations while maintaining a closed surface energy balance, which is commonly not achieved with observation data alone.