Lab 15
Air Masses
Classification of air masses
Fronts
Warm fronts
Stationary Fronts
A warm front separates a warm and humid air mass and a cold and dry air mass. The warm air mass will move over the colder
air mass because it is less dense.
A warm front occurs when a warm air mass moves into an area that was occupied by a cold air mass.
The temperature and the dew point tend to increase
The arrival of a warm front can also cause the wind direction to shift from the southeast to the southwest in the Northern Hemisphere and from the northeast to the northwest in the Southern Hemisphere.
Warm fronts will sometimes produce thunderstorms.
The atmospheric pressure decreases steadily.
Although the stationary boundary does not move, the warm and cold air masses along the boundary often move parallel to each other.
A stationary front is found in an area where a warm air mass and a cold air mass move past each other.
Cold Fronts
There is often some light patchy rain, and the dew point is high and steady.
Atmospheric pressure begins to decrease.
Before a cold front arrives, the temperature tends to be warm.
There tend to be wind gusts that shift directions.
A cold front occurs when a cold air mass moves into an area that was previously occupied by a warm air mass.
Polar:region. Polar air masses originate in high latitudes near Earth’s poles.
Arctic: Arctic air masses originate in high latitudes near Earth’s poles.
Equatorial: Equatorial air masses originate in low latitudes.
Continental: Continental air masses originate over land.
Definition: An air mass is a large body of air that has relatively uniform temperature and moisture conditions at any given altitude.
Formation: An air mass forms when a portion of the air in the lower atmosphere stays over a relatively uniform region of Earth’s surface, such as a large body of water, for several days.
Depending on the amount of moisture in the air and the speed of the cold front, the amount of precipitation can range from light to heavy.