Alaska's Weather and Climate

The air mass that exists over Alaska and Yukon Territory is one of the world's most interesting because a lot of action takes place within it. High mountains, volcanoes, moist Pacific air, the cold Arctic ice pack, the aurora and even the airplanes on the transpolar air route all play a role in what goes on in the air around and above our heads.

The Alaskan landmass separates the Pacific Ocean from the Arctic Ocean with the result, in part influenced by high mountain masses, that Alaska has three climatic zones. The Alaska Range in the south forms the boundary between regions of maritime and continental climate. Similarly, the Brooks Range divides regions of continental and Arctic Polar Basin climate.

Especially when the wind blows over Alaska from the south and southwest, the mountains have great influence. Warm moist air from the Pacific Ocean brings fog and low stratus clouds to the maritime zone. When the moist air tries to rise over the coastal ranges, it dumps much rain and snow (sometimes 50 feet in a single winter). The result in the most extensive glaciation anyplace in the United States.

Then as the somewhat dried air mass moves on northward to encounter the Alaska Range, it sometimes develops a highly turbulent motion--the consequence of the mountains of the Alaska Range being so high.

Except in such a special circumstance, the air in the lower part of the atmosphere undergoes little mixing with the air located above in the stratosphere. As the name implies, the stratosphere is a region of stratified air. The stratospheric air moves horizontally but not so much vertically. Though the air below, in the region called the troposphere, does get mixed up a lot, the stratospheric air is highly layered.

Because of the lack of mixing in the stratosphere, any aerosols or pollutants that enter it tend to remain there for days, or even months. Erupting volcanoes, exploding nuclear bombs and continuing ejections of industrial pollutants inject materials into the stratosphere. Also, the jets flying on the transpolar air route inject aerosols and form high cirrus clouds. Once there, these materials can circulate easterly around the earth or move into the high Arctic. The material slowly settles into the highly mixed tropospheric air below and eventually comes to ground level. The turbulent mixing that occurs because of the high Alaska Range accelerates the process and sometimes gives Alaska more than its proper share of the aerosols and pollutant materials.

One of the features of weather in the continental climate zone is the formation of height-extended cumulonimbus clouds which bring summer showers, lightning and forest fires to interior Alaska. On farther north, in the Brooks Range and beyond, stratus clouds again become the dominant cloud cover. Both they and sea ice are important factors in determining how much solar energy reaches the ground in the northern regions.

A particularly intriguing question about the air mass over Alaska is that regarding the effects of energy entering the top of the mass from the aurora and related phenomena. High electric fields associated with the aurora cause extremely high winds at the top of the atmosphere. These winds may create influence lower down, as may energy that comes to the atmosphere in other forms. Still, the amount of aurorally-related energy that enters at the top is comparatively very small, and its effects are largely unknown.