There are many components when it comes to understanding different types of
weather systems. When it comes to weather, many vital parts such as air masses are very important to understand. One might ask, what is an air mass? An air mass is a large body of air that has similar temperature and moisture properties (ww2010.atmos.uiuc.edu). When there are similar characteristics and temperature and humidity within an air mass this is called its source region. The source region is the original start of an air mass. For a source region to have similar characteristics, the surround environment must be of one. Also, there must be enough time for the source region to acquire the similar characteristics (Gabler). Some characteristics to determine a source region must be flat terrain, little wind and high pressure (www.uwsp.edu). There are six main types of air masses which are abbreviated by a first lower case letter and followed by a upper case letter. Gabler distinguishes the difference of each letter and each mass will be described. There are only 2 lower case letter to choose from the first being m, meaning maritime. Maritime means the air mass originates over the sea and is relatively moist. The other choice is c, meaning continental. Continental means the air mass originates over land and is therefore dry (Gabler). The following uppercase letter helps locate the latitude of the source region. There are four uppercase letters to help distinguish the regions, E,T,P,A. E stands for equatorial like the equator, the conditions are warm. T stands for tropical and its origins are the tropics so this is warm as well. P is for polar where the conditions can be quite cold and lastly is A which stands for Arctic air and is really cold. The following description of the different type of air masses will be concentrated more towards the air masses located in the United States and Canada but maps will be provided to show a globe perspective of the air masses as well as a more in depth chart on the air masses such as characteristics, accompanying weather and the source region. Continental arctic air masses, cA, (60°-90° N) (www.uwsp.edu) are very frigid and the frozen surface of the Arctic Ocean serves as the source region for this air mass. The conditions are very cold, very stable and very dry. Most of the time cA doesn't extend far enough to reach the Unites States but if so, the results can be damaging to vegetation. Most locations of this type of air mass are: the arctic ocean, Greenland, Antarctica, Alaska and Canada. The result of cA reaching the Midwestern to southeastern parts of the Unites States can be very seldom and record temperatures can often result (Gabler). Continental polar air masses ,cP, (40°-60° N or S) (www.uwsp.edu) are about the northern part of the United States. Locations of these types of masses are plains and plateaus of sub polar and polar latitudes. The conditions are subsiding and stable air. In the winter the air is cold, dry, clear and crisp. On rare occasions, a sliver of the cP can reach the Gulf of Mexico and some parts of Florida. This type of mass usually will stay on the east part of the United States due to atmospheric circulation but if it were to make it far west as Washington, California and Oregon it can cause great agriculture damage (Gabler). Maritime polar air masses, mP, are located at oceans between 40°-60° latitude. Characteristics are ascending air and general instability and the winters are mild and moist. In the winter months, the oceans tend to be warmer then the land. A common source region for mP is the Pacific Ocean. mP air is the source of many Midwestern snowstorms even after crossing the western mountain ranges. This is because when mP air meets an uplift mechanism such as colder, denser air or coastal mountain ranges the result is usually very cloudy with a lot of precipitation (Gabler). Maritime tropical air masses, mT, (15°-35° N or S) (www.uwsp.edu) are usually located at the Gulf of Mexico and the sub tropical Atlantic Ocean. Sometimes it can effect southeastern Canada. The winters where mT are located have warmer waters and the air is warm and moist, humid. Fog is a trademark condition with mT because when the warmer and moist air moves northward towards the Mississippi Lowlands, it will travel over cooler lands and the lower layers are chilled causing the dense advection fog. In the summer months, areas in the mT mass areas are warmer in temperature and the humid factor is moist. The other mT masses that are sourced over the Pacific Ocean are slightly cooler than the masses over the Gulf of Mexico. This mass is the result of the dry summers of southern California and the moisture in the mountains of the Pacific Coast (Gabler). The fifth type of air mass is continental tropical, cT,. For the United States the cT doesn't affect it very much and the source region is primarily located in deserts and dry plateaus of subtropical latitudes making the environment very hot and dry. The regions where it does effect the United States is a small area over the deserts of the southwestern United States (Gabler). Lastly, maritime equatorial, mE. The oceans that surround the equatorial oceans are the source regions for mE. The characteristics are ascending air and a very high moisture content (Gabler). In conclusion, these air masses that commonly influence weather in the United States are very important and vital to understand when trying to understand weather systems. If one learns about these air masses, then one would understand the importance of weather on this earth.