Climatic Effects on In-Situ Soil State Profiles Considering a Coupled Soil-Atmosphere Interaction Model

The influence of soil-atmosphere interactions on an unsaturated soil in water-limited environment is investigated using a coupled heat-water flow model with a balance of net solar energy at earth's surface. The paper also presents the governing equations for soil-atmosphere interaction analysis which, although important, are still rare in geotechnical applications. Numerical results were obtained by approximating the governing partial differential equations through a 1D finite difference scheme representing the soil as a two-layer system. Soil state profiles (temperature, moisture and suction) were predicted using daily meteorological data collected in France, from 2004 to 2005. Parametric analyses estimated the effects on soil state profiles caused by changes in initial conditions (soil temperature), hydraulic properties (saturated hydraulic conductivity), model geometry (upper layer thickness), ratio of reflected to incident solar radiation (soil albedo) and characteristics of meteorological data (sampling frequency). For the investigated site, the zone of seasonal fluctuations (ZSF) where the moisture and corresponding suction profiles is influenced by climatic conditions is about 1.5 m. The results also show that calculated average month meteorological values as daily inputs modify significantly the ZSF (about 100%). Predicted soil temperature profiles were in good agreement with measured values.