Field observations of soil temperature and water tension feedback effects on needle ice nights

Abstract

Numerous laboratory studies have indicated that thermal gradients may produce appreciable soil water movement in the absence of a strong suction field. In addition the soil water flow and thermal properties are physically interrelated. This paper presents field data taken during needle ice events at Vancouver, Canada, and yields an indication of the magnitude of interaction between the thermal and water flow properties. This feedback determines the state of soil frost hazard in a location where damage to plant material is produced by ice frost hazard in a location where damage to plant material is produced by ice needle growth. Further apparently anomalous interruption in the normal parabolic temperature-time pattern during radiation events is interpreted as the product of water flow down a thermal gradient.