Lecture
Air currents arising from the uneven distribution of pressure play a major role in the transport of air masses with different physical properties. These masses form in specific regions. The following types of air masses are of greatest importance in the formation of climates:
Arctic air;
Air of temperate latitudes;
Tropical air;
Equatorial air.
Arctic air forms over the ice fields of the Arctic; it is very cold air containing little water vapor. Its intrusion into temperate latitudes causes sharp and rapid temperature drops known as cold waves. The vertical extent of Arctic air is usually 2 km, sometimes up to 5 km. Cold waves can in some cases reach North America and even the shores of Florida.
Continental air of temperate latitudes over the territory of Russia forms from maritime air of temperate latitudes and Arctic air. Maritime air of temperate latitudes moves together with cyclones. Over the continents it is transformed into continental air. Such a transformation of air masses is called transformation.
Tropical air forms in tropical deserts and steppes from equatorial air and air of temperate latitudes. During the warm season, its formation centers (affecting the territory of Russia) are Central Asia, Northern China, Mongolia, and southern Russia. The intrusion of this air causes dry, hot weather accompanied by hot dry winds (sukhovei).
Equatorial air forms from the tropical air of the trade winds. This air is highly humidified and has a high temperature.
The physical properties of air masses do not remain constant; their properties change over time.
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