What Are The Four Types Of Air Mass?

When watching the weather forecast you have probably wondered what the lines with symbols which move across the map of your area resemble.

They are quite commonly used and not knowing what they mean can lead to confusion and like you are not getting the full story when it comes to the weather.

What Are The Four Types of Air Mass

These colored shapes and lines are used to give specific information about the future weather conditions, and they do this by specifically focusing on the movement of different air masses.

An air mass is a section of the air which is often very large and within this area there will be a general consistency with humidity as well as the temperature.

What Is The Definition Of An Air Mass?

As previously mentioned, the definition of an air mass is a portion of the air which is large and is quite uniform in its temperature as well as its humidity and other similar characteristics.

These characteristics will often originate from the water or perhaps the land that is below the air mass. These air masses can go up to thousands and thousands of miles in size and can go many miles up into the atmosphere.

What Are The 4 Different Types Of Air Masses?

Experts on the weather look at air masses and classify them based off of factors like their humidity and their temperature.

There are further methods of classifying an air mass and putting it into different categories and these are often based on whether they occur over land or over water.

There are 4 main types of air mass that will affect the weather in North America and these 4 types are; maritime tropical (which is signified with mT), continental tropical (using cT), maritime polar (signified with mP), and continental polar (which uses cP).

The rest of this article will be focused on placing more detail on these different types of air masses, as well as shedding light on the types of air masses that are still present globally but do not form in North America and will very rarely affect the weather in this region.

The Source Regions And The Characteristics Of Different Air Masses

The main method in which meteorologists use to classify where air masses is the area in which they originate and these are split into 4 different source regions.

These 4 different regions will usually be large and flat and have consistent formations this includes formations like oceans and deserts and not including hills or mountains.

The reason for this is because the speeds of the wind will need to remain low enough to make sure the air will gain the attributes necessary for one of these regions to be able to form an air mass. 

When these air masses eventually take form, the wind will be able to move this air mass into a different new region and doing this will create different weather conditions like storms for example.

These are seen as characteristics of the air mass and are seen as the attributes of the air mass clashing with the attributes of the area it is entering like the conditions of the temperature or the humidity.

The main aspect which the temperature will affect is the air pressure. This means that denser air will tend to be cooler and will have a much higher pressure.

The inverse it of course true with less dense air tending to be more warm and subsequently having a lower pressure.

This means that air masses which are warm or tropical have a lower air pressure and those which are cold or polar will have a higher air pressure.

As can be expected the humidity of a specific air mass will depend highly on whether it has been formed over land or if it was formed over water.

The maritime air masses will then be more likely to have more humid conditions because they have formed over oceans when the water in them have evaporated.

And then continental air masses will inversely tend to be much more dry since they have formed over land where there will be much less exposure to the large bodies of water which create humid conditions.

The rest of this article will go in-depth on exploring the different terms and types of air masses which are used in discussing forecasts to help you understand what each of the terms means and how you can apply this knowledge when discussing the weather.

If you want more details on how different air masses act and what they mean, keep reading to get the information you need!

Polar Air Masses

Polar air masses can be categorized by the latitude at which they form being usually between 50 and 60 degrees.

It is possible for this type of air mass to be able to form over water, the most common source of polar air masses is over regions like Siberia and the northern sections of Canada.

These air masses can also be classified by how they are especially cold and dry, because of this characteristic dryness, polar air masses will tend to have far fewer clouds than other types of air masses.

A polar air mass when being spoken about in a shortened way will be abridged to a capital “P”.

Arctic Air Masses

These are some of the coldest air masses and as their name suggests they tend to form in the polar regions. When shortening the name for this type of air mass it will either be shortened to “A” for the Arctic variety or “AA” for the Antarctic type of air masses.

What Are The Four Types of Air Mass (1)

Tropical Air Masses

In comparison to the previous type of air mass, tropical air masses have a tendency to be much warmer and sometimes even hot. These air masses tend to form around 25 degrees latitude in reference to the equator.

Tropical air masses will develop either over land or water and when they are spoken about they are usually shortened to a “T”. The places where tropical air masses are most likely to form will either be in the Gulf of Mexico, as well as northern Mexico.

They can also form in the southwestern regions of the US. Tropical air masses are known for how they move across different lands and will usually cool at a much more quick rate than other air masses.

Because of this quick cooling they are much more likely to result in weather conditions like precipitation or storms.

Equatorial Air Masses

As the name of this type of air mass suggests, an equatorial air mass will usually originate along the Earth’s equator at a latitude of 0 degrees, and due to the nature of the equator, these air masses tend to have a very hot temperature.

There are no equatorial air masses which are classified as continental due to the equator being almost completely devoid of many land areas and because of this, this type of air mass will very rarely affect those who live inside the US.

Continental Air Masses

A continental air mass will tend to develop in either the north or the south of the equator and will be at somewhere between 25 to 60 degrees of latitude.

These types of air masses can be classified due to being distinctly dry and are known for tending to form over large expanses of land areas.

The way meteorologists represent this type of air mass is by using a lowercase font “c” specifically, the reason for this is because the temperature of an air mass is seen as more of a relevant factor and therefore is made to stand out more.

Maritime Air Masses

As previously mentioned, a maritime air mass will tend to be humid due to the evaporation of the water which is below them when they are formed and this is why they are referred to using a lowercase “m” by meteorologists. 

So when a meteorologist wants to classify an air mass they will combine the symbol for a temperature of a land mass with the humidity as well as its origin and this will be used to make a symbol to portray it.

The next sections will show the 4 types of air mass which are the most common in Northern America.

Continental Polar

These will be larger air masses which have formed over the regions of northern and central Canada as well as Alaska.

These Continental polar air masses are characteristic of American winters and are known for bringing clear, dry, and most importantly cold air.

They have a much more mild affect during summer months, but they can often clash with a maritime tropical air mass and this will often lead to the creation of storms.

Continental Tropical

In contrast, continental tropical air masses are most common in summer and are characterized by dry and hot air and will be most common in the southwestern and the northern regions of Mexico.

These types of air masses will often move into the northeast and will give the Great Plains more dry and hot weather, but they usually have a much smaller range than different air masses.

Maritime Polar

These maritime polar air masses have a strong presence in the west coast of the US, and they form above the cold waters of both the North Atlantic and Pacific oceans and will create distinctly cool and humid air which will lead to weather conditions like fog, rain, as well as cold temperatures even within the summer months.

Maritime Tropical

During the summer months these air masses are most likely to form over the Gulf of Mexico as well as the Atlantic and have a characteristic warm heat as well as humidity.

This type of air mass is most likely to move into the southeastern sections of the US and will begin with them humid and hot conditions which will lead to rain as well as thunderstorms. They will continue northeast until they dissipate.

In the western regions, the Pacific Ocean will also create some maritime tropical air masses which will then affect the weather on the west coast, but they will lose much of their moisture and humidity after they move over the mountain ranges in the coastal regions.

During the winter months these air masses can lead to heavy snow and rain especially in the southwestern regions of the US

Other Types Of Air Masses

Using the system of shortening the different types of air masses you can learn about other types of air masses which are either less common in the US or more common in other parts of the world.

But we hope that this guide will help you feel more informed next time you are watching the forecast!

https://youtu.be/TcZZVcP6EBY
Andrew Capper