What's the difference between arctic and polar air?

Late fall and winter bring the coldest air of the year to NCWV. Most cold days are due to polar air moving south out of Canada. However, near-record low temperatures are caused by arctic air. So, what is the difference between the two?

The main difference is where they come from. You may have guessed that the farther north (closer to the north pole) the air, the colder it is. You would be right! Arctic air sits close to or over the north pole. It is the driest and coldest air that visits our area. The reason it is so cold is due to the lack of sunshine there. What little sun this region does get is hard to warm up the air. A few reasons. One, it is usually covered in ice. This reflects the meager heat from the sun. Two, the low sun angle (sun not getting high in the sky) gets scattered since it has to move through more of the atmosphere. This means that even less makes it to the ground.

Polar air is a frequent guest here in the Mountain State. It usually comes from the southern half of Canada. It is also cold, but it gets a little more sunshine than farther north.

NCWV sits in what we call the 'middle latitudes'. Roughly from the northern border of the U.S. into the southern part of the country. This is where air masses mix. You may notice that it can be mild, even in the winter, or it can be very cold. This is due to not only cold air moving in from then north, but warmer air moving in from the south. Air masses mix due to low pressure systems in the mid-latitudes. It is not uncommon for it to get warm ahead of storm systems from southerly winds bringing sub-tropical air from the Gulf of Mexico. However, on the back side of storm systems, the winds turn to the north and pull in colder Canadian air.

Remember, low pressure spins counter-clockwise (in the northern hemisphere). This brings warmer air head of low pressure systems then colder air on the back side with northerly winds.