Mary Beth has taught 1st, 4th and 5th grade and has a specialist degree in Educational Leadership. She is currently an assistant principal.
What Are Air Masses?
Did you know that all air is not the same? Yes, it is always invisible. Yes, it is always made of oxygen, nitrogen and other gases. However, it is not always the same temperature, nor does it always have the same level of moisture or humidity. These different types of air are known as air masses.
Imagine the planet covered in blankets. Each blanket horizontally covers different parts of the Earth. Okay, so the planet isn't actually covered in blankets, but it is covered in air masses. Just like air masses, blankets are not the same. Some are thick and wooly, while others are light and fluffy. You will feel differently depending on which kind of blanket you are under, just like you will feel differently depending on which type of air mass you are under.
Land or Water?
The first way to categorize a type of air mass is to see what it is located over. Is it located over land or is it located over the sea? Air masses that are over land are called continental air masses because they are over continents. They tend to be on the drier side. Air masses that are over the ocean are called maritime ('mar' is actually a prefix for anything water, like marine biology). These air masses are moister, which makes sense because they are over water.
Now it gets a little more complicated than land or water. Another determining factor when categorizing an air mass is how far the land or water over which the air mass is hovering is from the equator. Scientists have grouped these into three different places: arctic, polar and tropical. Arctic, as you might guess, are the coldest air masses. They are located over the North and South poles. Polar air masses are also cold, but not as cold as the Arctic air masses. Tropical air masses are the warmest, and are located in the areas that are about 25 degrees north or south of the equator.
The Six Types
Okay, so now that you know the terms for land or water, as well as the different source regions, you have enough information to determine the six types of air masses. These are: continental arctic (cA), maritime arctic (mA), continental polar (cP), maritime polar (mP), continental tropical (cT), and maritime tropical (mT). Easy enough, huh?
Believe it or not, you already know what each air mass is like solely based on its name. Let's take cA, for example. Remember - continental air masses are dry and arctic air masses are really cold. Therefore, the cA air mass is dry and very cold. Try one on your own - mT. If you guessed that it is a moist (maritime) and warm (tropical) air mass, you got it!
Keep in mind that air masses don't always behave in a predictable manner. They don't stay in the same place and they move quite a bit. When continental and maritime air masses collide, extreme weather (i.e. hurricanes) can take place.
Sometimes, you will see an air mass with an extra letter - either a W or a K. These letters describe what is happening when an air mass moves. So if you see a W, this means that the air is warmer than the land it is over. A K stands for cold (well, C actually stands for cold, but that already stands for continental, and that would just be confusing, so they went with K) air moving across warmer land.
Air masses are horizontal shapes of air that have similar characteristics. Continental air masses are dry and are over land; maritime air masses are moist and are over water. Air masses are also defined by how far the land or water they're hovering over is from the equator.
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