Review of heat and water movement in ®eld soils

Coupled heat and water transport in soils has enjoyed extensive focus in soil physics and hydrology and yet, until recently, there has never been a satisfactory comparison of water vapor ̄uxes measured in the ®eld with theory. At least two factors have led to this, ®rst, most of the experimental work has been laboratory oriented with steady state boundary conditions imposed and second, there have been relatively few ®eld experiments to test the existing theory. In this paper we review a new theoretical development which explains ®eld observations of water vapor movement. The diurnal warming at the land surface leads to an expansion and contraction of the soil air as it warms and cools resulting in a convective (or `̀ advective'') transport of water vapor. This mechanism has important consequences for the transport of any vapor in the soil air near the landatmosphere interface. # 1998 Published by Elsevier Science B.V. All rights reserved.