This writing will go over the comparison and contrast between polar and arctic air. I will first point out that arctic is a common misspelled word. I have often seen the first “c” missing in the word arctic. Both polar and arctic air represents fairly cold air. They both originate at higher latitudes and are especially prevalent in the late fall, winter and early spring. Both air masses can bring much colder temperatures into the middle latitudes. This air can be ushered in behind cold fronts bringing a huge drop to the temperature. Both polar and arctic air modify as it moves toward the lower latitudes since the land surface and water surface is generally warming moving toward the equator. Sometimes the terms polar air and arctic air will be used interchangeable but there are some differences between these air masses. Arctic air tends to be colder than polar air. In the air mass source regions, the temperatures of arctic air can reach far below 0 F, such as in the -30’s to -40’s below zero. Polar air tends to not start out as cold as this. Polar air can be below 0 F but tends to not get down to the extreme cold temperatures that arctic air does. As a consequence, polar air modifies faster to warmer temperatures as it moves into the middle latitudes. In the central and southern U.S., polar air can drop temperatures into the 40’s, 30’s, 20’s and 10’s degree F for example. Arctic air though can drop temperatures into the 10’s, 0’s, and below 0 degree F temperatures in these same regions. Arctic air tends to be drier than polar air. Arctic air tends to develop over the harsh frozen lands and ice covered regions such as in the Northern Canada and Siberia. A land surface or ice surface can cool off more than liquid water surface. Polar air can not only form over land surface but also can develop over ocean regions. Because the water ocean surface is warmer, polar air does not cool to the extreme cold temperatures that arctic air does. Polar air that develops over land can have similar characteristics to arctic air except it does not cool off as much. This can occur when this air mass develops over a region closer to the mid-latitudes, such as in southern Canada instead of Northern Canada. It can also be because the air did not have as much time to cool off before being brought down into middle latitudes. Arctic air can pool and cool over Northern Canada, frozen arctic waters and Siberia for weeks before it is brought down into the middle latitudes. This extra time allows the air mass to get extremely frigid. Arctic air tends to be drier than polar air. Since arctic air is colder, this in turn causes the dewpoints to have to be colder. Since polar air (such as maritime polar) can develop over the oceans, it tends to have much higher dewpoints as compared to arctic air that develops over “frozen deserts”. Arctic air is much more likely to set record low temperatures as compared to polar air. There is not always an easy distinction between what qualifies as polar air and what qualifies as arctic air in borderline cases due to the characteristics that polar and arctic air due have in common. As polar or arctic air move toward the equator they both will modify. Arctic air will eventually modify to polar-like temperature and moisture characteristics. Polar air will eventually modify if it has the chance to move far enough toward the equator that the temperature may not drop much behind the cold front. Developing arctic air may not have enough time to drop to the extreme cold temperatures before being brought into the middle latitudes. This air mass can act more like polar than arctic air. Arctic air developing early in fall or late in spring will not cool down as much since the sun is still shining in the higher latitudes this time of year. This can cause an air mass developing over Siberia and Northern Canada to act more like polar air. The terms polar and arctic are often used interchangeable to mean cold air originating from high latitudes. For example, terms like polar express, polar vortex and arctic surge are basically using the term polar or arctic to mean cold air in the higher latitudes. |