Air Masses

In meteorology, an air mass is a vast body of air with essentially consistent temperature and humidity conditions at any given altitude. The limits of such a mass are defined, and it can span hundreds or thousands of kilometres horizontally and as high as the troposphere’s top (about 10–18 km [6–11 miles] above the Earth’s surface). The temperature and moisture properties of a large, reasonably homogeneous land or sea surface are acquired when the atmosphere comes into contact with it over a long enough period of time. The beginnings of the Earth’s major air masses are at polar or subtropical latitudes. The middle latitudes are essentially a zone of polar and tropical air mass alteration, interaction, and mixing.

Categorisation of Air Masses

Air masses are traditionally classified into four basic source regions based on latitude. Polar (cold), Arctic (very cold), Equatorial (warm and humid), and Tropical (warm). Continental Polar, maritime Polar, continental Tropical, and maritime Tropical are the most common air mass types in the United States.

Air Mass Categorisation of the USA

Continental Polar (cP):

Continental Polar (cP) air occurs across large land areas such as Central Asia and northern Canada during the colder months of the year. It’s most likely stable, and it’s usually free of condensation forms. This type of air mass creates limited convective stratocumulus cloud formations with scattered light rain or snow showers when heated or moistened from the ground with significant turbulence. As the cP air mass descends to lower latitudes in the summer, significant continental heating rapidly alters the coolness and dryness of the air mass. The rule is that cumulus clouds form during the day, but the upper-level stability of the air mass usually prevents rain showers.

Maritime Polar (mP):

Maritime Polar (mP) air masses form over both the Northern and Southern hemispheres’ polar regions. They usually have a lot more moisture in them than cP air masses. When air is pushed to ascend mountain slopes or is caught up in cyclonic activity as it moves inland in the middle and high latitudes, substantial precipitation may occur (see cyclone).

Continental Tropical (cT):

The continental Tropical (cT) air mass develops in arid or desert regions in the middle and lower latitudes throughout the summer. It’s hot in general, but because the moisture content is so low, the vigorous dry convection rarely reaches the condensation threshold. The cT is the driest of all the air masses, and it is responsible for the world’s subtropical desert belt.

Maritime Tropical (mT):

Throughout the year, the maritime Tropical (mT) is the most important moisture-bearing and rain-producing air mass.In the winter, it moves poleward and is cooled by the ground surface. As a result, fog or low stratus or stratocumulus clouds, drizzle, and limited visibility define the weather. The occurrence of severe frontal and convective rains is ensured by a steep lapse rate aloft in cyclonic activity regions. The properties of the mT air mass over the oceans and in cyclonic activity zones are essentially the same in summer as they are in winter. However, over warm continental locations, the air mass is powerfully heated, resulting in widely scattered and locally heavy afternoon thunderstorms instead of fog and low stratus clouds.

Characteristics of air mass:

• At any given height, it has fairly constant temperature and humidity conditions.
• It stretches thousands of kilometres across the Earth’s surface and can reach from the ground to the stratosphere.
• Winds transport weather conditions from one location to another when they move air masses.
• Maritime air masses are humid and come from the ocean. Dry air masses that occur over land are known as continental air masses.

Conclusion

An air mass is a big volume of air that has a temperature and humidity that are more or less constant across its entirety. The region over which an air mass forms is what determines its properties and gives it its name. When an air mass remains in the same location for a longer period of time, it has a greater chance of absorbing the characteristics of the surface that it is above.