Now that we discussed what air masses are. We are going to dive into each type in a little more detail. In case you missed the Weather 101 episode with a general overview of the five types of air masses, you can view it HERE.
The first air mass we will look at is Continental Polar (cP). With winter not too far away and with us starting to see more effects from this particular air mass, I thought this would be a good one to start with.
Characterizations of a Continental Polar Air Mass
The main characterizations that describe an air mass are typically the temperature and the moisture content. For the continental polar air mass the temperature is cold and the moisture content (dew points) are very low.
The atmospheric profile is typically very stable and limits the amount of cloud cover and precipitation experienced. Stability leads into our next topic which is the weather experienced with continental polar air masses.
Development and Source of Air Mass
A continental polar air mass is created up in the high subpolar latitudes of the United States. This encompasses much of northern Canada. If snow cover is present, parts of the northern United States can contribute to the development of this air mass.
Snow cover is KEY to developing these colder air masses. The cold snow pack insulates the ground, and keeps the heat from the surface from being released. This allows the air mass to get colder and colder and grow deeper and deeper. Eventually this bottled-up cold air is released southward by the dipping jet stream.
Early on in the winter season watch the Northern U.S. and Canadian provinces closely for snow depth of snowpack, and keep track of the temperatures. They will most likely grow colder, especially with a fresh layer of snow. You will be witnessing the birth of a continental polar air mass.
What Type of Weather Can You Expect?
During the winter, you can expect not much in the way of cloud cover or precipitation. The cold temperatures limit the amount of the moisture carried by the air mass. Moisture return during the winter is also weaker, so as the air mass moves south it doesn’t have much moisture to work with to produce precipitation.
During the transition months like spring or fall, light precipitation is possible on the outer edges of the air mass due to the presence of more moisture ahead of it. The precipitation typically will occur on the outer edges of the air mass, because it is where the fronts are located. Most of the lift occurs due to the front.
Modification of the Air Mass
As the air mass pushed south it starts to change or modify some of its characteristics. The dew points (moisture content) stay about the same. The temperatures will start to increase slowly due to several factors.
Those factors are warmer soil temperatures, a shallower air mass, higher sun angles, and a lack of snow cover.
After a particularly cold stretch of weather the soil moisture temperature is much lower. This allows the modification of the air mass to occur at a slower rate. As the air mass starts to warm, the depth of the air mass starts to thin out as the cold air is slowly eroded away.
In future episodes, we will dive into the 4 other types of air masses. Catch other episodes of Weather 101 HERE!