AIR MASSES, FRONTS AND CYCLONES
Air masses are large volumes of air that have relatively uniform temperature, humidity, and pressure characteristics over a vast area. They play a crucial role in determining weather patterns and climate across different regions by transporting heat and moisture from one area to another
An air mass is a large body of air with horizontally uniform properties in terms of temperature, humidity, and pressure. These properties are acquired from the underlying surface over which the air mass forms and can extend for thousands of kilometres.
1.Large Bodies of Air with Uniform Temperature and Moisture Characteristics: Air masses are typically several hundred to thousands of kilometres wide and can be several kilometres thick. They form when air remains stationary over a large, homogeneous region, such as an ocean, desert, or ice-covered area, for an extended period. During this time, the air acquires the temperature and moisture characteristics of the underlying surface. For example, an air mass forming over a warm ocean will be warm and moist, while one forming over a cold, dry landmass will be cold and dry.
2.Formation of Air Masses: Air masses form in source regions, which are typically large, flat areas with relatively uniform surface conditions. These regions must have stable atmospheric conditions that allow the air to remain in place long enough to acquire the surface characteristics. Common source regions include the tropics, polar regions, oceans, and continental interiors. The classification of air masses is based on their temperature and moisture content, such as Maritime Tropical (mT), Continental Tropical (cT), Maritime Polar (mP), and Continental Polar (cP). For example, Maritime Tropical (mT) air masses, which form over warm oceans like the Gulf of Mexico, are warm and humid, while Continental Polar (cP) air masses, forming over cold land areas like Canada, are cold and dry.
The characteristics of an air mass depend on its source region and the nature of the surface over which it forms. These characteristics can change as the air mass moves away from its source region and interacts with different environments.
1.Homogeneity of Temperature and Humidity: One of the defining features of an air mass is its uniformity in temperature and humidity over its horizontal extent. This homogeneity is due to the prolonged interaction with a specific surface type in the source region, where the air mass remains relatively undisturbed. For instance, a Continental Arctic (cA) air mass originating over the Arctic ice cap will be extremely cold and dry throughout its expanse, while a Maritime Tropical (mT) air mass over the subtropical Atlantic Ocean will be uniformly warm and moist.