Air masses are large portions of air that have relatively homogeneous internal conditions of temperature, pressure and humidity, influenced by the region where they are formed.
The place of formation of the air mass is called region of origin, it is in this place that the air mass will acquire its characteristics of temperature, pressure and humidity. Therefore, an air mass that forms on a frozen surface, such as Antarctica, presents typical characteristics of this region, that is, low temperature, high pressure and low humidity.
When moving, the air masses gradually lose their characteristics of temperature, pressure and humidity originated at the time of their formation. This displacement always occurs in the direction of high pressures to low pressures.
The troposphere (place of movement of air masses) is not a homogeneous layer. In it, there are basically three distinct types of air masses that differ according to the latitude on which they were formed, and can be classified as equatorial, tropical or polar. Among this classification, it still differs in continental (formed in continental areas) or oceanic (formed in oceanic areas).
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Equatorial masses – their formation occurs at low latitudes, in the region close to the equator, between 5° North and 5° South. They present high temperatures, when formed in oceanic areas they are humid; if formed in continental regions, they are less humid.
Tropical masses – their regions of origin are in areas close to the tropics of Capricorn and Cancer, between latitudes 25° and 30° in both the northern and southern hemispheres. They are very humid air masses, however, if formed in continental areas, they are normally dry.
Polar masses – they form in regions close to the South and North poles, always at latitudes above 50° and, due to these aspects, are extremely cold. The continental polar is cooler and drier; the ocean is wetter.
By Wagner de Cerqueira and Francisco
Graduated in Geography
Would you like to reference this text in a school or academic work? Look:
FRANCISCO, Wagner de Cerqueira e. "Masses of air"; Brazil School. Available in: https://brasilescola.uol.com.br/geografia/massas-ar.htm. Accessed on June 27, 2021.
