With fall being a temperature transition month, we start to see more cold fronts swinging through. Why is this you ask? It is due to the production of air masses particularly of the continental polar type (more on this in a bit). In this segment of Weather 101 we are going to discuss air masses.
What are they?
An air mass is a section of the atmosphere with similar moisture and temperature characteristics. These giant blobs of air move around with the general circulation of the atmosphere. The leading edge of these air masses are where fronts are located. Our cold fronts hang around the leading edge of the continental polar air mass typically. Our warm fronts are typically located along the edge of the advancing maritime tropical air mass.
We’ve already mentioned a few of the names of these air masses, but how are they named?
Naming an Air Mass
There are 5 types of air masses that we can see enter the United States. These are named after the moisture and temperature characteristics of the air mass.
We rarely see Arctic air masses make it into the lower 48. They typically modify into a Polar air mass in Canada before descending into the United States. This doesn’t necessarily mean that we never see them.
|Arctic (Extremely Cold)||Continental (Dry)|
|Polar (Cold)||Maritime (Moist)|
The 5 Types
|Air Mass Name||Air Mass Abbreviation|
You may notice that there is both maritime and continental descriptors for both Polar and Continental temperatures, but not for Arctic. Maritime Arctic (mA) DOES NOT EXIST. This is because the extremely cold temperatures of the Arctic air mass does not allow water to stay liquid. It freezes over and becomes a drier Continental air mass.
Air Masses and Unsettled Weather
When these air masses collide the weather is sure to become unsettled. Weather is driven completely by temperature imbalances. When these air masses with different moisture and temperature characteristics meet they can create different types of weather.
Cold air shovels warm air upward increasing the instability which can lead to storms. Dry air shovels moist air upwards leading to increased instability as well.
We will dive into more detail with these 5 types of air masses in future episodes of Weather 101. We will explore where each of these come from, and what type of weather they can bring when they move over us.