This week we have experienced record breaking cold in many locations across our viewing area. Why is this cold record breaking? The short answer is that we are in the grip of an Arctic air mass.
Characterizations of a Continental Arctic Air Mass
|Extremely cold||Extremely dry|
All air masses are characterized by temperature and moisture characteristics. The arctic air mass is classified by its extremely low dew points (bone dry) and its frigid/bitterly cold temperatures. As far as stability is concerned, this air mass is very stable and also very dense. In fact if the high pressure associated with it at the surface is strong enough, the air mass will push south without any help from the jetstream.
Development and Source of Air Mass
Arctic air masses develop in the, surprise, arctic latitudes. Some specific birthplaces are Siberia and Eastern Alaska. Other locations include the Canadian Provinces of Yukon and the Northwest Territories. All these locations are typically known for being bitterly cold during the winter months. This makes these locations the perfect breeding ground for this particular air mass.
There are several factors that allow arctic air to grow and deepen in these locations. They are the general lack of incoming solar radiation, the abundant snow/ice packs, and the continuous emission of longwave radiation from the surface. The combination of these ingredients can create temperatures that range from 30°F – 60°F below zero!
What Type of Weather Can You Expect?
This air mass brings brutally frigid and dry conditions for the most part. In fact the skies are mostly clear with sunshine seen through much of the day. Some freezing fog can develop from time to time at the surface. The weather looks deceivingly nice and warm. In reality, however, the conditions are brutal and deadly.
One such example of a location that frequently experiences this type of air mass is northern Alaska. Specifically we are going to look at an airport site in Utqiaġvik, AK. This city was formerly known as Barrow, AK until 2016.
The early evening temperature for the airport site at the time of this photo was a balmy -42°F! Definitely this location is in the grasp of a continental arctic air mass. Notice that the skies for the most part are very blue and clear. There is a little bit of either diamond dust (suspended ice crystals) or ice fog in the distance.
Air Mass Modification
As the arctic air mass plows south, it starts to modify as it encounters warmer landmass and increased moisture. This change happens very slowly due to the extremely dry and cold nature of the air mass. The arctic air becomes more polar and the moisture content of the it increases slowly as well.
Instead of clear skies, cloudy skies are now possible in the wake of the cold air. Snow also becomes a better possibility as the moisture slowly increases as well. Although as you have seen this week, the snow ratios start to increase over 10:1. This is due to the lack of the moisture content.
Coldest of All the Air Masses?
You may think that arctic air masses take the crown when it comes to the coldest, but in reality the crown goes to the continental antarctic air mass (cAA). Why you might ask? The arctic is frozen ocean surrounded by land masses, and the antarctic is landmass surrounded by frozen ocean. The ice pack temperatures cannot drop as low as the landmass temperatures due to the slightly warmer ocean water underneath the Arctic Circle.
How much colder? The average temperature of the north pole during the winter is around -40°F while the average winter temps of the south pole is around -76°F. That is 36 degrees colder on average!