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Transcript of Air Masses
Air masses can have different densities.
Just like how oil and water have different densities...
Different masses do not mix.
...and do not mix.
The density of air can change!
Factors That Can Change Air Density:
Classes of Air Masses
Abbreviated as "mT".
Maritime Tropical air masses form over tropical oceans, such as the South Pacific or the Gulf of Mexico.
They often bring warm, humid weather.
Air masses form over a desert or a tropical land area such as Mexico.
abbreviated as "cT".
They bring hot, dry weather.
mP air masses form over oceans of arctic regions. They bring cool, wet weather with them as they move south.
abbreviated as "mP".
Air masses form over cold land areas, such as northern Canada or Alaska, and bring cold, dry weather.
abbreviated as "cP".
cA air masses form over snow and ice covered portions of the Arctic. They bring bitterly cold weather as they move south.
abbreviated as "cA".
While an air mass is passing over a region, that region experiences air-mass weather; for the most part, the same weather conditions will prevail from one day to the next.
When air masses meet, storms are formed at their boundaries. Meteorologists call these boundaries "fronts".
Fronts are named by the air mass that is advancing into the "territory" of another air mass.
Cold air is denser than warm air, so it wedges under the warm air at the front, lifting it off the ground and pushing it back. This violent uplifting of warm, moist air can produce thick clouds and severe weather, often without warning.
When a warm air mass moves into territory occupied by a cold air mass, the lighter warm air flows up and over the heavy cold air. The weather begins with cirrus clouds, which are soon followed by other types of clouds, which come lower and lower to the ground. Eventually a light, continuous rain or snow begins.
Sometimes, neither air mass can displace the other, and they both become stationary. The weather caused by a stationary front is similar to the weather caused by a warm front, but it usually lasts for several days.
Cold fronts move faster than warm fronts. When a slow-moving mass of warm air begins to climb over a stationary mass of cold air, a warm front is produced. However, a second cold air mass may slide under the warm air and completely lift it off the ground! When the fast-moving cold front overtakes the slower-moving warm front. it forms a Y-shaped front called an "occluded" front. The weather produced is a combination of that produced by warm and cold fronts.
Classes of Air Masses