The Arctic is the aerial crossroads of the world.
This is not only due to the shorter arctic routes between
some of the major cities of the world, but also because
flying weather over the Arctic is generally better than
that encountered over the familiar ocean routes. To
understand some of the important weather and
problems of the Arctic, you must understand the broad
underlying causes of the arctic climate.
TIONS.From our previous discussion of climatic
controls, we have seen that the most important factor
that determines the climate of an area is the amount of
energy it receives from the Sun. During the winter
much of the Arctic receives little or no direct heat from
the Sun. The cold winter temperatures common in the
Arctic result from a lack of the Suns energy.
The Sun is not the only factor responsible for the
arctic climate. Two other factors, the land-sea-ice
distribution and mountain barriers, contribute to the
tremendous variation in climate at different points of
Hemisphere, the water features include the Arctic,
North Atlantic, and North Pacific oceans. These bodies
of water act as temperature moderators since they do
not have large temperature variations. A major
exception occurs when large areas are covered by ice in
winter. The land features are the northern continents of
Eurasia, North America, the island of Greenland, and
the Canadian Archipelago. As opposed to the water
areas, the land areas tend to show the direct results of
the extremes of seasonal heating and cooling by their
seasonal temperature variations.
Mountains. The arctic mountain ranges of
contribute to the climate and air mass characteristics of
mid-latitudes, restrict the movement of air from west to
east. During periods of weak circulation, the air is
blocked by the ranges and remains more or less
stagnant over the area. It is during these periods that the
characteristics of the underlying surface. Thus, these
areas are air-mass source regions, and they are
particularly effective as source regions during the
winter when the surface is covered with snow and ice.
The Greenland ice cap is essentially a mountain
range more than 10,000 feet above mean sea level. It
restricts the movement of weather systems, often
causing low-pressure centers to move northward along
the West Coast of Greenland. Some of the largest rates
of falling pressure in the world (other than hurricanes
and tornadoes) are recorded here. The deep, low centers
that move along the west coast of Greenland are
primarily responsible for the high winds that are
recorded occasionally in that area.
At times, winter temperatures in the Arctic are
unusually high. This situation is brought about by deep,
low centers moving into the Arctic, coupled with
compression of air (the Foehn effect) as it often blows
down off the sloping edges of the ice caps, primarily the
Greenland ice cap.
ARCTIC AIR MASSES.The moisture content
of air masses that originate over land is low at all
altitudes in the winter. The distinction between air
masses almost disappears during the summer because
of the nearly uniform surface conditions over the arctic
and subpolar regions. The frozen surface thaws under
the influence of lengthened or continual daylight, the
snow melts from the glaciers and pack ice, the ice melts
in the lake areas in the Arctic, and the water areas of the
polar basin increase markedly. Thus, the polar area
becomes mild, humid, and semimaritime in character.
Temperatures are usually between freezing and 50°F.
Occasionally, strong disturbances from the south
increase the temperature for short periods. Daily
variability are slight.
During the winter months, air masses are formed
over areas that are completely covered by ice and snow.
The air masses are characterized by very cold surface
air and a large temperature inversion in the lowest few
thousand feet. Since the amount of moisture the air can
hold depends on the air temperature, the cold arctic air
is very dry (low absolute humidity). The air mass that
originates over oceans does not have a surface
temperature inversion in the winter, the surface air
temperature is warmer, and there is a corresponding
increase in the moisture content of the air. It is during
movement inland of moist air from the warmer waters
that most of the rather infrequent arctic cloudiness and
precipitation occurs during this season.
During the summer months, the large expanse of
open water and warmer temperatures in the Arctic
result in increased moisture. Consequently, the largest
amount of cloudiness and precipitation occurs during
these summer months.