Abstract
A numerical model of boundary layers between soil and atmosphere is developed, which simulates soil-water movement during drying in a nonhomogeneous bare soil. A modified and extended form of Philip and de Vries' equations for soil-water and heat flows is deduced in the present study. The results of numerical simulation are compared with the data obtained from field observations in a volcanic ash soil in Japan called Kanto loam. The computed profiles agree fairly well with those of the field observations for a simulated period of 35 hr., following rain. The results are summarized as follows: directions of total moisture fluxes are upward above a depth of 35 cm; upward total moisture fluxes appear to decrease with depth from the soil surface to 35 cm; directions of total moisture fluxes are always downward below 35 cm; isothermal liquid fluxes contribute much to the total moisture fluxes in all stages of the computation at every depth; isothermal vapor fluxes are negligible; thermal moisture fluxes are negligible below a depth of 30 cm, where diurnal soil temperature variations are quickly damped; directions of thermal moisture fluxes appear downward in the daytime and upward at night; magnitudes of thermal liquid fluxes are larger than those of thermal vapor fluxes.
Published Version
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