Abstract
At hot, dry soil surfaces, water vapor density increases sharply from under the ground to the surface air layer, although the vapor moves upward across the surface against its density gradient. The machinery by which the counter-gradient flow of vapor occurs seems to be a kind of convection which is driven by the large temperature difference between the soil surface and the air next to it. More work neeeds to be done, however, to clarify the way these characteristic vertical profiles per se are produced. It can be inferred from these results that the rate of evaporation from bare soil during its third stage is controlled by the profiles of soil water and temperature, and is scarcely influenced by the humidity and wind speed in the surface air layer.
