Meteorological elements, primarily solar radiation and air temperature, influence surface and subsurface temperature by affecting the rate at which heat is transferred to or from the atmosphere and the ground. Solar radiation is probably the single most important factor. Differences in average annual ground temperature between the north and south of Canada are due mainly to the amount of solar energy absorbed at the surface throughout the year. Seasonal and daily changes in solar radiation impose a cyclical variation on both air temperature and ground surface temperature. Other meteorological factors such as wind or rain can cause significant local variations.
Snow is probably the second most important factor affecting ground temperature.
This influence is due not only to its well known insulating properties but also to the moisture it provides to the ground during the thaw period. Vegetation can exert a similar insulating effect, protecting the underlying ground from weather extremes that cause high rates of heat transfer to and from the atmosphere. Other terrain features such as slope orientation, can have significant effects. In general, slopes with a southern exposure have a higher average ground temperature than north-facing slopes. There are numerous publications available on the effect of terrain features on ground temperature 3 .