to Download a VIDEO CLIP on The Midnight Sun. (685KB AVI)One example of this modification of weather by the mountain barrier is the Brooks Range. It keeps air from the Arctic Ocean from moving southward and keeps the arctic climate zone from the interior. Similarly, the Chugach, Wrangell, Aleutian and Alaska mountain ranges keep air from moving northward. They also help to dry the air before it reaches the interior of the continent.
There are others factors that affect Alaska's climate zones. Some of these are air temperature, water temperature, cloud coverage and the wind and air pressure. One example of this is that the temperatures along the coast are much more temperate with less extremes than the temperatures inland. The reason for this is that warm air holds more water vapor than cold air. Therefore warm air holds more precipitation such as rain or snow. Water temperatures change very slowly and therefore, the climate in coastal areas changes very little. Let's take each of the four climatic zones separately.
The maritime climate zone includes the Southeast, the Northern Gulf Coast and the Aleutian Chain. In these areas the temperatures are mild because of the water, as mentioned above. It is fairly warm in the winter and cool in the summer. Because of the mild temperature, there is a great deal of precipitation. The coast gets 50 to 100 inches annually and up on the mountain slopes, they get 400 inches. They have a great many storms from the west and the southwest and with these storms come strong winds in the Aleutian Islands and on the Alaska Peninsula. Amchitka Island's weather station recorded the windiest weather in the state. The cause of this has to do with the rotation of the earth and the tendency for two different high and low pressure fronts to attempt to equalize. Some of the winds are so strong and occur often enough to be given names. These winds are the Chinook, Taku and Williwaws.
The Chinook winds happen in unusually warm weather. When they happen, they can cause a thaw in the middle of the winter. They also cause a lot more things, like power outages and property damage. This happens especially in the Anchorage area. Homes have recently been builtin the Chugach Mountains where the chinook winds have always blown. On April l, l980, a Chinook caused $25 million in damages and the whole area was declared a disaster area. Some areas had no power for 60 hours. It has only been recently that these winds can be predicted by meteorologists, and they only do it about 55 % of the time. It has been found that a warm wind has to originate in the Prince William Sound and has to have a speed of 55 miles per hour or more to cross the Chugach Mountains, which are 3,500 feet high. So now they can sometimes warn the residences to prepare for the Chinook in Anchorage.
The Taku happen very suddenly and they come down the ice caps behind Juneau and Douglas. They are very fierce. Because of coming from the ice caps, they are very cold and can reach up to 100 miles per hour. It has been known to send a 2 x 4 piece of wood crashing through the wall of a building.
The Williwaw are also sudden gusts that reach high speeds very quickly. They can reach up to 113 miles per hour. The way they happen is that the wind builds up on one side of the mountain and then quickly spills over into the other side. They can be devastating to the mariners in Alaska.
On to the second zone, the transition zone. Is has two separate zones. One is between the coastal mountains and the Alaska Range. This includes Anchorage and the Matanuska Valley. It is interesting that their summer temperatures are even higher than those of the maritime zone. They also have colder winter temperatures and not as much precipitation. The other transition zone is the west coast from Bristol Bay to Point Hope. Their temperatures are somewhat different than Anchorage. They have cool summer temperatures, at least cooler than the maritime area. The winters are cold. This is due to the sea ice in the Chukchi and Bering Seas.
The majority of Alaska falls into the continental climate zone. It covers all except the coastal edges and the Arctic Slope. It is known for extreme temperatures and very low precipitation. They don't have many clouds in this area and therefore have more warming from the sun in the long days of summer and stay more cool from the long long winter nights. Since they have very few clouds, they also have very little precipitation. Most of the moisture is lost crossing the mountains.
The last zone is the Arctic zone. This area is south of the Brooks range of mountains. It has very cold winters and cool summers. There is so little precipitation that is can be compared to desert regions. The winds come from the ice pack in the northeast. In the summer it is very often cloudy and just the opposite in the winter - clear and cold. Once again, the cold air doesn't pick up much precipitation. The ground is very marshy-like and has numerous lakes. This is because of permafrost. Permafrost is a condition that occurs when the ground stays frozen for two or more years. Actually, it lies under the entire Arctic regions up to 2,000 feet deep. This condition affects construction in Alaska. Care must be taken because a structure built on permafrost may cause it to thaw and then the building will sink.
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Text by: The Alaska Almanac 19th Edition,
America the Beautiful: Alaska,
From Sea to Shining Sea: Alaska
Video Clip by: Alaska Video Postcards
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