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Continental tropical air masses are extremely hot and dry. [7] Arctic, Antarctic, and polar air masses are cold. The qualities of arctic air are developed over ice and snow-covered ground. Arctic air is deeply cold, colder than polar air masses. Arctic air can be shallow in the summer, and rapidly modify as it moves equatorward. [8]
When the air reaches the polar areas, it has cooled by radiation to space and is considerably denser than the underlying air. It descends, creating a cold, dry high-pressure area. At the polar surface level, the mass of air is driven away from the pole toward the 60th parallel, replacing the air that rose there, and the polar circulation cell ...
Rising air also occurs along bands of low pressure situated just below the polar highs around the 50th parallel of latitude. These extratropical convergence zones are occupied by the polar fronts where air masses of polar origin meet and clash with those of tropical or subtropical origin in a stationary front. [2]
For lake-effect rain or snow to form, the air moving across the lake must be significantly cooler than the surface air (which is likely to be near the temperature of the water surface). Specifically, the air temperature at an altitude where the air pressure is 850 millibars (85 kPa ) (roughly 1.5 kilometers or 5,000 feet vertically) should be ...
Atmospheric pressure is the total weight of the air above unit area at the point where the pressure is measured. Thus air pressure varies with location and weather . If the entire mass of the atmosphere had a uniform density equal to sea-level density (about 1.2 kg/m 3 ) from sea level upwards, it would terminate abruptly at an altitude of 8.50 ...
The polar vortex is a large area of low-pressure and cold air surrounding both of the Earth’s poles, according to the weather service. It always exists near the poles.
(cA is continental arctic; cP is continental polar; mP is maritime polar; cT is continental tropic; and mT is maritime tropic.) A weather front is a boundary separating two masses of air of different densities, and is the principal cause of meteorological phenomena. In surface weather analyses, fronts are depicted using various colored lines ...
It deposits drier air, contributing to the world's great deserts. The horse latitudes, or torrid zone, [20] is roughly at the 30th parallel and is the source of warm high pressure systems. As the hot air closer to the equator rises, it cools, losing moisture; it is then transported poleward where it descends, creating the high-pressure area. [21]