Heat and Water Transfer at the Land-Atmosphere Interface – Interweaving Experimental and Modeling Approaches

Abstract:

In the absence of vegetation, evaporation occurs entirely from the soil and can lead to considerable water losses. Considering the increase of water limited environments throughout the world and their potential for expansion over the coming years, it is critical that we are able to properly understand and model evaporation. Evaporation is affected by atmospheric conditions (e.g., humidity, temperature, wind velocity, solar radiation) and soil thermal and hydraulic properties (e.g., thermal and hydraulic conductivity, porosity), all of which are strongly coupled. However, for most conventional models, many of these mechanisms are crudely parameterized and inconsistent with current physical understanding due to the complexity of the problem in field scenarios and the scarcity of field or laboratory data capable of testing and refining energy and mass transfer theories. In this work, we investigated different physical processes that are often overlooked in models of flux exchange and how these processes may become significant in modeling arid and semi-arid environments. A non-isothermal model that allows for the coupling of single-phase (gas) two-component (air and water vapor) atmospheric flow and two-phase (gas, liquid) two-component (air and water vapor) flow in porous media was modified to better account for dry soil conditions. Numerical results were tested with precision experimental data. Results demonstrate that proper coupling of the thermal and mass flux processes allows us to better understand vapor transport and phase change processes that control shallow subsurface soil moisture and ultimately improve models predicting mass and energy fluxes.