Weather Topics   Temperature Inversions Maritime Climate Interior Climate Pressure Systems Solar Radiation Precipitation Optical Phenom. Arctic Weather Facts Min. Temps. < -90°F (Siberia & Greenland) Max. Temps. > 100°F (Interior locations) Avg. Temps 0°F to 20°F Avg. Precip. 10 to 20" Avg. Snowfall 5 to 15 inches Air Masses Maritime polar & Continental Solar Reflection Up to 90% in snow and ic-covered areas Nearest Permanent Weather Station to Pole Eureka, Canada (690 miles away) Optical Phenomena Clear skies and subzero temperatures produce spectacular optical displays in the Arctic. Haloes occur around the sun when light is refracted through ice crystals. Sun dogs are luminous spots on both sides of the sun that occasionally occur with a halo. The fata morgana is a complex mirage in which distant flat objects appear to have tall cliffs, columns, and pedestals. A superior mirage occurs when an image of an object appears above the actual object, due to the downward refraction of light in cold, dense air. Ice blink refers to a white glare seen on the underside of low clouds indicating the presence of ice which may be beyond the range of vision. Water sky refers to the dark appearance of the underside of a cloud layer when it is over a surface of open water. A corona is a ring of deflected light that surrounds the sun or moon, sometimes forming a colorful disk with the sun or moon at its center. A fog bow is similar to a rainbow, but without any colors due to the very small size of the water droplets.

Weather in the Arctic

The Arctic climate is quite variable. It includes both polar maritime (influenced by the ocean) and continental (influenced by large land masses) climate subtypes. The Greenland ice sheet and the Arctic Ocean maintain cold temperatures throughout the year, but the tundra-covered coastal fringes warm up each summer for a brief period. The main climate constant in all Arctic areas is the extreme fluctuation of incoming solar radiation. Long, dark winters followed by short summers with continuous sunlight are responsible for the unique living and growing conditions of the far north. Spring and summer sun brings enough energy to sustain life, but not enough to melt all the frozen water or the frozen ground, hence the ubiquitous snow and ice of the Arctic landscape.

Temperature

Arctic winters are long and cold, and summers are short and cool. Temperatures vary with latitude, ice and snow cover, and proximity to the ocean. Ice covers most of the ocean surface year-round, causing subfreezing temperatures much of the time. The Arctic is a major source of very cold air that moves toward the equator, meeting with warmer air in the middle latitudes and causing rain and snow. Minimum temperatures of - 90° F are reached in Greenland and northern Siberia; maximum temperatures of about 23° F to 36° F are common on the ice sheet, and highs of 70°F 100° F are common on land areas.

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Inversions

In winter, Arctic weather is dominated by the frequent occurrence of inversions (when warm air lies above a colder air layer near the surface). The inversion layer decouples the surface wind from the stronger upper layer wind. For this reason, surface wind speeds tend to be lower in winter than one might expect. In summer, inversions are less frequent and weaker, and arctic weather patterns are dominated by the movement of low pressure systems (cyclones) across Siberia and into the Arctic Basin.

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Maritime climate

Maritime climate conditions prevail over the Arctic Ocean, coastal Alaska, Iceland, northern Norway and adjoining parts of Russia. In these areas, winters are cold and stormy. Summers are cloudy but mild with mean temperatures about 50°F. Annual precipitation is generally between 20 and 40 inches (largely winter snowfall) and there are about six months of snow cover.The Arctic Ocean, which receives relatively warm north-flowing currents from the Atlantic and Pacific, acts as a moderating influence, especially on the surrounding shores and islands.

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Interior climate

The interior, continental climates have more severe winters than maritime climates, although precipitation amounts are less due to the low moisture-holding capacity of cold air. In these regions, permafrost (permanently frozen ground) is wide-spread and often of great depth. In summer, only the top 3 to 6 feet of ground thaw. Since the water cannot readily drain away, this "active layer" often remains waterlogged. Although frost may occur in any month, long summer days usually provide three months with mean temperatures above 50° F, and at some stations in the continental interiors highs can exceed 90° F. Tundra climates are those where one or more of the warmest months has an average of over 32° F but not over 50° F, the ground is free of snow for a short period, and a sparse and primitive vegetation cover is present. Ice-cap climates have average temperatures year round that are below freezing, the growth of vegetation is impossible, and a permanent snow-and-ice cover prevails.

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Pressure Systems

In many Arctic and subarctic regions, the weather is controlled by semipermanent low pressure systems that are weakly developed in summer, but stronger in winter. The most important low pressure systems are the Icelandic Low and the Aleutian Low. In winter, eastern Eurasia is dominated by the semipermanent Siberian High. High pressure is also prevalent over the Canadian Arctic Archipelago during the cold season. Except for a few coastal locations, Arctic winds are generally weaker and less prevalent than those of Antarctica.

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Solar Radiation

The low sun angle in the Arctic means that even minor topographic features, such as low hills, can cause major differences in climate at the local level by shading. Even though the Arctic receives a large amount of solar energy in summer, the high reflectivity (albedo) of snow and ice surfaces keeps absorption of solar energy low. Therefore, the heat gained during the long summer days is small and highly dependent on surface properties such as topography and albedo. For instance, wet tundra and bare ground (with low albedo) absorb more solar radiation than do high-albedo ice sheets. Similarly, wet snow absorbs more radiation than dry snow. Solar radiation is small or absent in winter; in snow-covered areas as much as 90 percent of the incoming solar energy is reflected back to space.

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Precipitation

Climatically, many high Arctic locations are considered cold deserts -- that is, they receive (with local exceptions) less than 10 inches of precipitation annually. Indeed, some areas of the Arctic, such as Peary Land in northern Greenland, are drier than many tropical deserts. Generally, precipitation amounts are higher the farther south one travels in the Arctic region. Most precipitation in the Arctic takes the form of snow, which falls mainly during the autumn and the early spring.

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