Air Masses Flashcards
Definition of weather.
Weather (8)
The short-term condition of the atmosphere, as compared to climate, which reflects long-term atmospheric conditions and extremes.
What are the important measurable elements that contribute to the weather?
Temperature, air pressure, relative humidity, wind speed and direction, daylength, and Sun angle are important measurable elements that contribute to the weather.
What is Meteorology
The scientific study of the atmosphere, including its physical characteristics and motions; related chemical, physical, and geological processes; the complex linkages of atmospheric systems; and weather forecasting.
What is Air Mass?
Air mass
A distinctive, homogeneous body of air that has taken on the moisture and temperature characteristics of its source region.
Each area of Earth’s surface imparts its temperature and moisture characteristics to overlying air. The effect of a location’s surface on the air creates a homogenous mix of temperature, humidity, and stability that may extend through the lower half of the atmosphere.
How do we classify air masses?
We classify air masses according to the general moisture and temperature characteristics of their source regions
How do we designate moisture levels on air masses?
Moisture is designated m for maritime (wet) or c for continental (dry).
How do we designate temperatures of air masses.
Temperature is directly related to latitude and is designated A for arctic, P for polar, T for tropical, E for equatorial, and AA for antarctic.
Characteristics of Continental polar (cP) air masses
- Continental polar (cP) air masses form only in the Northern Hemisphere
- Most developed in winter and cold-weather conditions.
- Major players in middle- and high-latitude weather, as their cold, dense air displaces moist, warm air in their path, lifting and cooling the warm air and causing its vapour to condense.
- An area covered by cP air in winter experiences cold, stable air; clear skies; high pressure; and anticyclonic wind flow. The Southern Hemisphere lacks the necessary continental landmasses at high latitudes to create such a cP air mass.
Characteristics of Maritime polar air masses (mP)
- Maritime polar (mP) air masses in the Northern Hemisphere sit over the northern oceans.
- Within them, cool, moist, unstable conditions prevail throughout the year.
- The Aleutian and Icelandic subpolar low-pressure cells reside within these mP air masses, especially in their well-developed winter pattern
What are the two maritime tropical (mT) air masses that influence North America?
The mT Gulf/Atlantic and the mT Pacific
What creates the humidity experienced in North American east and Midwest?
The humidity experienced in the North American East and Midwest is created by the mT Gulf/Atlantic air mass, which is particularly unstable and active from late spring to early fall.
How dose the mT Pacific air mass affect the western US
the mT Pacific is stable to conditionally unstable and generally lower in moisture content and available energy. As a result, the western United States, influenced by this weaker Pacific air mass, receives lower average precipitation than the rest of the country.
What happens the longer an air mass remains stationary over a region?
The longer an air mass remains stationary over a region, the more definite its physical attributes become.
What happens to an air mass as it migrates from source regions?
As air masses migrate from source regions, their temperature and moisture characteristics slowly change to the characteristics of the land over which they pass.
What is the lake effect?
As below-freezing cP air passes over the warmer Great Lakes, it absorbs heat energy and moisture from the lake surfaces and becomes humidified. In what is called the lake effect, this enhancement produces heavy snowfall downwind of the lakes into Ontario, Québec, Michigan, northern Pennsylvania, and New York
