Why are Canadians air masses considered to be dry air masses?
http://www.met.tamu.edu/class/atmo202/Dir-surface/surface-stu.html
To understand why Canadian air masses are generally considered to be dry, we need to look at their origin and characteristics. Canadian air masses refer to large bodies of air that originate from the high latitudes of Canada, typically the central and northern regions.
1. Source Region: Canadian air masses originate in the high latitude regions, predominantly over land masses, such as the Arctic and Subarctic regions of Canada. These regions are characterized by extensive ice and snow cover as well as frigid temperatures. Since there is limited access to warm, moist air sources like oceans, the air masses remain relatively dry.
2. Air Mass Trajectory: As Canadian air masses move southward, they generally do not pass over significant bodies of water. Unlike maritime air masses that travel over oceans, Canadian air masses tend to traverse over land masses and experience less moisture exchange from evaporation. Hence, they retain their dry characteristics.
3. Continental Polar (cP) Air Mass: The main classification of Canadian air masses is continental polar (cP). cP air masses are formed when cold, dry air from the Canadian high latitudes moves southward. Due to their source region and trajectory, cP air masses have limited exposure to moisture, resulting in their overall dryness.
It's important to note that while Canadian air masses are generally considered dry, there can still be variations in moisture content depending on the specific weather conditions and location they encounter during their southward journey.