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Tropical air masses have lower pressure because hot air rises and cold air sinks. Those that develop over land (continental) are drier and hotter than those that develop over oceans, and travel poleward on the southern periphery of the subtropical ridge. [5] Maritime tropical air masses are sometimes referred to as trade air masses. Maritime ...
Those that develop over land (continental) are drier and hotter than those that develop over oceans (maritime), and travel northward on the western periphery of the subtropical ridge. [16] Maritime tropical air masses are sometimes referred to as trade air masses. [17]
In a cold occlusion, the air mass overtaking the warm front is cooler than the cold air mass receding from the warm front and plows under both air masses. In a warm occlusion, the cold air mass overtaking the warm front is warmer than the cold air mass receding from the warm front and rides over the colder air while lifting the warm air. [2]
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 and symbols, depending on the type of front. The air masses separated by a front usually differ in temperature and humidity.
In order 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 the altitude where the air pressure is 850 millibars (or 1.5 kilometres (0.93 mi) altitude) should be 13 °C (24 ...
Orographic or relief rainfall is caused when masses of air are forced up the side of elevated land formations, such as large mountains or plateaus (often referred to as an upslope effect). The lift of the air up the side of the mountain results in adiabatic cooling with altitude, and ultimately condensation and precipitation.
This effect is virtually confined to land regions as the ocean retains heat far longer. In the polar regions during winter, inversions are nearly always present over land. A warmer air mass moving over a cooler one can "shut off" any convection which may be present in the cooler air mass: this is known as a capping inversion. However, if this ...
The distance that an air mass travels over a body of water is called fetch. Because most lakes are irregular in shape, different angular degrees of travel yield different distances; typically, a fetch of at least 100 km (60 mi) is required to produce lake-effect precipitation. Generally, the larger the fetch, the more precipitation produced.