Four major masses of air lie over different parts of the world. The tropical maritime mass is warm and moist; the tropical continental mass is hot and dry. The polar continental mass is cold and dry, and the polar maritime mass is cold and wet. These air masses are blown around by high-level winds, and their interactions have a major influence on the world’s weather. The kind of weather experienced depends on the nature of the air mass — tropical masses bring warm, humid weather, and the polar masses tend to bring snow. In places where these masses meet, the weather can be very changeable indeed.
Weather is controlled by a variety of factors. One of the most important is Earth’s air masses. Air masses are huge parcels of air with specific characteristics. What’s interesting about the characteristics of an air mass is that, not only do they describe the air mass, but they also tell you where you can find that air mass on Earth.
Let’s look at the different types of air masses found on Earth to see how this works. Air masses can be divided into two main categories based on whether they are found over land or water. If the air mass is found over land, this is a continental air mass. If the air mass is found over water, this is a maritime air mass. This makes sense: continental air masses occur over the continents, maritime air masses occur over the water, or marine environments. These categories are represented by a lowercase ‘c’ for continental or ‘m’ for maritime.
The source region of the air mass helps us classify it even further, and for this, we have three categories. Arctic air masses occur over arctic regions, like Greenland and Antarctica. Polar air masses occur a little bit farther from the poles, like in Siberia, Canada and the northern Atlantic and Pacific Oceans.
Finally, tropical air masses occur in the tropics, so along the equator and over Mexico and the Southwest U.S. Makes sense, right? These categories are represented by the first letter of the source region, but this time we use an uppercase letter. So, ‘A’ stands for arctic, ‘P’ for polar and ‘T’ for tropical. That’s pretty easy to remember!
Each source region can also be either continental or maritime, and to represent this, we simply combine the category letters. This gives us six total types of air masses on Earth: maritime arctic (mA), maritime polar (mP), maritime tropical (mT); and continental arctic (cA), continental polar (cP) and continental tropical (cT).
Air Masses and Weather
You can understand a lot about weather from air masses just by looking at the name. Maritime air masses are going to produce moist weather because they occur over oceans, and oceans are filled with water! The air blowing over the ocean regions, either arctic, polar or tropical, picks up that moisture as it travels along. In maritime arctic and polar regions, this moist air is cool (as you probably expected), and the maritime tropical air mass produces the warm, humid conditions you would expect along the tropics, like Florida and the Caribbean.
In contrast, continental air masses produce dry weather. This is because the continents just can’t compete with the oceans when it comes to moisture! The continental arctic and polar air masses produce dry, cold weather in the winter and pleasant weather conditions in the summer.
Picture Credit : Google