People in the Mountains - Mountain Geography: Physical and Human Dimensions - page 503

FIGURE 10.10 An example of an alpine pastoral settlement, occupied seasonally, on sunny south-fa-
cing adrêt slopes, above the upper Rhine River Valley, Grisons, Switzerland. (Photo by C. Stadel.)
The quality of sunlight received in the mountains changes with altitude, with an in-
crease in the proportion of short-wave radiation received, particularly ultraviolet (UV),
because of the lower concentration of absorptive gases. This results in radiation burn-
ing of animal and plant tissue, producing sunburns, greater probability of skin lesions
and cancers, and damage to crops at higher altitudes.
WIND
Wind is common at all scales in and around mountains, often with velocities and dura-
tions exceeding those found in other environments. Generally, average wind velocities
and gustiness increase with altitude, around exposed ridges, and in confined valleys.
The effects, particularly those on people, are: accentuation of cold and dryness; trans-
port of sensible heat or cold, gases, liquids, and particulates; and physical pressure
on objects. Wind aids the evaporation of moisture from surfaces like skin and leaves,
which, in turn, causes cooling and drying (i.e., wind chill and dessication or “freeze dry-
ing”). On the positive side, this helps regulate heat in animals and plants, preventing
damage from overheating. On the negative side, it may accentuate freezing and excess-
ive drying, damaging exposed skin, crops, and trees. Wind, through warming and drying
and transport effects, is a major factor in causing mountain forest fires and comprom-
ising control and mitigation efforts. Winds may have cooling or warming effects through
the transport of colder or warmer air, as when cold air blows of a glacier surface to val-
ley locations in a katabatic wind, which can limit agriculture and settlement downslope
from glaciers. Earlier, we noted the foehn, Chinook, and zonda, downslope winds that