Mountain Climate - Mountain Geography: Physical and Human Dimensions - page 88

In establishing the relationships between mountain mass and the heat balance, con-
tinentality, latitude, amount of cloud cover, winds, precipitation, and surface condi-
tions must all be considered. Persistent cloud cover during summer can prevent a large
mountain mass from showing substantial warming. A heavy snowcover can also retard
the warming of a mountain area in spring because of surface reflectivity and the amount
of initial heat required to melt the snow. The high Sierra Nevada of California is relat-
ively warm compared with other mountain areas, in spite of heavy snowfalls, partially
because the extreme clarity of the skies over this region in late summer allows maxim-
um reception of solar energy. In general, the effect of greater mountain mass on climate
is somewhat like that of increasing continentality. The ranges of temperature are great-
er than on small mountains (i.e., the winters are colder and the summers warmer), but
the average of these temperatures will generally be higher than the free air at the same
altitude. The effective growing climate, especially, is more favorable at the soil surface
than in the free air, owing to higher soil temperatures, particularly when there is a high
percentage of sunshine (Yoshino 1975).
Generally, the larger the mountain mass, the higher the elevation at which vegetation
grows. The most striking example is in the Himalaya, where plants reach their absolute
highest altitude (Chen et al. 1985). In the Alps (where the influence of mountain mass,
Massenerhebung, was first observed), the timberline is higher in the more massive cent-
ral part than on the marginal ranges (Imhof 1900, in Peattie 1936: 18). More locally,