An air mass is a vast body of air that acquires uniform temperature and moisture characteristics from its source region. Arctic air is a specific type of air mass, classified by meteorologists as continental Arctic (cA), which originates from the highest latitudes on Earth. This air mass is defined by its extremely cold temperatures and low moisture content, representing the most frigid air available to move across the Northern Hemisphere.
The Source and Definition of Arctic Air
The source region for Arctic air lies within the high-latitude Arctic basin, generally north of 60 degrees latitude, encompassing Northern Canada, Siberia, and the Arctic Ocean. Formation requires a prolonged period of intense cooling, facilitated by the long, dark polar nights of winter. Minimal solar radiation reaches the surface, allowing heat to radiate continuously from the Earth’s surface into space.
The presence of extensive snow and ice cover across the source region also helps maintain the frigid temperatures by reflecting solar energy. This sustained cooling under a stable high-pressure system allows the air to take on the characteristics of the surface, becoming exceptionally cold. The meteorological classification is continental Arctic, or cA, where the “continental” designation signifies its formation over land or ice, resulting in extremely low moisture content.
Physical Properties and the Polar Distinction
Arctic air is characterized by distinct physical properties that make it unique among air masses. Temperatures within the core can be low, often dropping into the range of -30°F to -60°F (-34°C to -51°C) in its source region. The frigid temperatures result in high air density because cold air molecules are packed more closely together than warm air molecules. This density helps the air mass move as a coherent, heavy mass.
The air is also exceptionally dry, with low dewpoints, because the intense cold severely limits the atmosphere’s capacity to hold water vapor. This dryness contributes to the clear skies often observed in the center of an Arctic high-pressure system.
It is important to distinguish this from Polar air masses (P), which form further south, typically between 40 and 60 degrees latitude. While Polar air is cold and dry, Arctic air is significantly colder, originating over regions perpetually covered in ice and snow. The extreme cold of Arctic air allows it to maintain its frigidity far into the mid-latitudes, making it responsible for setting record-low temperatures.
How Arctic Air Influences Local Weather
When a surge of dense Arctic air pushes south, often channeled by the jet stream, it dramatically impacts the weather of any region it encounters. The most immediate effect is a rapid temperature drop, sometimes occurring over just a few hours as the cold front boundary passes. The accompanying winds enhance the wind chill factor, making the extreme cold feel more severe and increasing the risk of cold-related health issues.
The high density of the Arctic air mass causes it to hug the ground, creating a stable atmosphere and often resulting in a strong temperature inversion. This inversion layer features colder air trapped near the surface with warmer air above it, which suppresses vertical air movement and cloud formation.
When this dry, frigid air moves over the warmer waters of large lakes or the ocean, it picks up moisture and heat. This process leads to the formation of localized weather phenomena, such as lake effect snow, where the air mass destabilizes and drops significant snowfall downwind of the water body. The arrival of Arctic air is frequently associated with blizzards, as the clash between this extremely cold, dry air and warmer, moisture-laden air masses creates an intense weather system.