Relationship of ground temperatures to air temperatures in forests

Abstract

Ground temperatures differ from air temperatures because of effects of vegetation and humus, other site characteristics, and snow cover. For engineering work, ground surface temperatures may be estimated from the more readily available air temperatures through the use of a single parameter, the n-factor, to represent these effects. In the Mackenzie valley, n-factors have been calculated from measurements of air and ground temperatures at 27 diverse, natural sites. Generally, the n-factor for the thawing (spring-summer) season is higher in more open areas than in shady forests with thick moss. At a particular site, the n-factor for the freezing (fall-winter) season is usually lower than the corresponding n-factor for the thaw season, because of the reduced impact of air temperatures and solar radiation on the ground due to snow cover. One application of n-factors is the calculation of the depth of soil that thaws each year, called the active layer.