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Tuesday, September 16, 2014 - 10:42am

What Is The Difference Between An Arctic And A Polar Air Mass?

Weather Talk

POSTED: Monday, January 6, 2014 - 1:03pm

UPDATED: Monday, January 6, 2014 - 1:25pm

Yet Another Arctic Airmass Produces "Historic" Super Freezing Temperatures To Our North

When you hear the words "arctic" and "polar do you shiver with images of igloos, dangerous freezing winds, Polar Bears and dog sleds racing over the snow and ice covered tundra?  My thoughts exactly!  I used to think there was not much of a difference between Arctic and Polar air, it was all just too cold!  In this "Weather Talk" blog I will tell you that you that yes indeed there are many differences between the two air masses.

This cold season, which began back in October 2013, the U.S.,  has had multiple invasions of arctic & polar air masses. The latest dove in Sunday and is impacting a large area of the United States for the next couple of days. . Temperatures today Monday are predicted only to top out at -15 in Minneapolis where all the schools in the entire state of Minnesota are closed Monday and -11 in Chicago. Wind chills will range from -40º to a “Historic” -65º + in Minneapolis! Your bare skin will freeze in a matter of minutes at -50º! These are very dangerous conditions!
The Borderland just caught the edge of that super chilled air mass so we will top out at a rather mild, cold 46º in El Paso Monday Afternoon. Which , by the way is the coldest day of the year. Yes I know it is only January 6th!

Let us first look at the definition of an air mass.

An air mass is a huge body of air with similar temperature and moisture properties. The types of air masses formed on Earth are determined by where they originate.

Temperature and moisture content are the two main features that define an air mass. In the horizontal plane, temperature and humidity are essentially consistent in the layers of the air mass. Vertically, the general trend in an air mass is cooling, but the temperature and moisture will remain fairly consistent. The height of the air mass is greater with warm air masses. Cooler air masses are shallower. In addition to the temperature and humidity in an air mass, the stability of the air can change over time.

In this “Weather Talk” I will only touch on the air masses that impact our cold season.

Arctic, Antarctic, and polar air masses are all cold.

The qualities of arctic air are developed over ice and snow-covered ground. Arctic air is deeply cold, colder than polar air masses. Arctic air can be shallow in the summer, and rapidly modify as it moves towards the equator. Polar air masses develop over higher latitudes over the land or ocean, are very stable, and generally shallower than arctic air. Polar air over the ocean and loses its stability as it gains moisture over warmer ocean waters.

Arctic air starts out in northern Canada and Siberia. This frigidly cold and dry air in Siberia sometimes is able to push over the North Pole and spill into the North American continent. Arctic air has the same characteristics as Polar air except it is colder with even lower dew points. This very cold air many times is formed when a high-pressure area becomes nearly stationary over Eastern Alaska, the Yukon, Siberia or northern Canada. Because of the massive amount of snow and ice covered land, the lack of solar warmth and constant radiational cooling, the loss of radiation from the Earth's surface the air will progressively become colder and colder. Temperatures, like we have seen the past couple of days can reach -30 degrees F to -60 degrees F. The Arctic air builds and eventually the super cold air spills into Southern Canada and the United States. When the Arctic air makes it into the Southern U.S.., it modifies enough to be become Polar air behind the edge of the cold front.

Continental polar or continental arctic air masses are cold, dry, and stable. These air masses originate over northern Canada and Alaska as a result of radiational cooling, when all the heat is lost into space, replaced by cooling surface air. The Continental polar air masses move southward, east of Rockies into the Plains, then eastward. Continental polar or continental arctic air masses are marked by surface high pressure, cold temperatures, and low dew points.

Maritime polar air masses are cool, moist, and unstable. Some maritime polar air masses originate as continental polar air masses over Asia and move westward over the Pacific, collecting warmth and moisture from the ocean. Some Maritime polar air masses originate from the North Atlantic and move southwestward toward the Northeast States. The latter air mass generally is colder and drier than the Maritime polar off of the Pacific.

Now this current "super freeze" of most of the northern and central states is a Continental arctic air mass, the coldest of them all. Minneapolis is expected to pop to a high of 2º by Tuesday and 12º by Wednesday. Chicago will improve to 4º Tuesday and 18º by Wednesday.  I know the folks to our north know the difference between an "Arctic" and a "Polar" air mass first hand. We knew it first hand back in the beginning of February 2011 when we had 4 mornings of below zero temperatures.  Thankfully we do not  too often feel the full impact of an arctic air!

I once again like most of us, should count our blessings weather wise for living right here in the Borderland.

Chuck DeBroder, Chief Meteorologist
KTSM, NewsChannel 9, NBC, El Paso, TX
cdebroder@ktsm.com
www.facebook.com/pages/Charles-DeBroder/
www.twitter.com/ Chuck DeBroder NC9 @wxchuckNC9

(Image. MGN Online)
 

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