Close observers of Antarctic skies are presented with a bewildering variety of cloud shapes and colors. Uunobstructed panoramas stretching to the horizon, providing a unique opportunity for viewing atmospheric and weather-related phenomena. Scientists who study cloud formations see a complicated picture; one that bears clues about the atmosphere, the climate, and approaching weather.

Clouds are made of tiny water droplets, ice crystals or both. The storms and clouds we think of as weather are concentrated in the lower seven miles or so of the atmosphere known as the troposphere. Clouds can serve as excellent indicators of changing weather. In general, flat clouds indicate stable conditions while piled-up clouds mean unstable air. The frigid temperatures of Antarctica's interior mean that little or no water vapor is held in the air, which can inhibit cloud formation, hence the clear skies typically observed at the South Pole. However, along the coast disturbances become more frequent and cloud-filled skies more common due to the maritime influence and polar circulation patterns.

Three Main Types of Clouds

Cirrus Thin, white feathery or wispy clouds, usually separated or detached. Highest of all clouds in tropopause, they form at 30,000 feet or more in the sky. They are composed primarily of ice crystals. Cumulus Flat-based, billowing clouds with vertical doming. Often the top of cumulus clouds have a "cauliflower-like" appearance. Cumulus clouds are most prominent during the summer months. Stratus Thin, layered clouds, often occurring as continuous or rippled sheets which cover large portions of the sky. Stratus clouds are frequently gray and thick. Other common cloud types Cirrostratus clouds are high, thin clouds that have a milky-white appearance. Cirrocumulus clouds are delicate clouds appearing in bands or ripples. Altostratus clouds are blue-gray or whitish in color. They are thinner and higher than stratus clouds and are formed by water and ice particles. Altocumulus clouds are mid-altitude "cottony-like" clouds, often oval or elliptical in shape, with gray undersides. Nimbostratus clouds are dark gray clouds often associated with steady precipitation. They occur in thick, continuous layers. Stratocumulus clouds often occur as dark, heavy rolls which form in bands or columns across the sky. Cumulonimbus clouds are taller, towering versions of cumulus clouds, which are often associated with thunderstorms. Their height can range from two to five miles.