Kristine Proseus, age 12, of Lansing, Mchigan, for her question:

What is meant by a polar wind?

The weather man often refers to this unwelcome visitor during the winter season. As its name suggests, a polar wind blows from the polar region. North of the equator, this is the Arctic and it howls down on us bringing winter storms sometimes from the north or northeast but usually from the northwest. Like all winds, of course, it is a sweeping current of moving air. But this air has been sitting on the snow and ice of the Arctic land and sea. For months the sun does not rise to warm the earth that normally warms the air above it. 'Masses of cold air tend to contract and become dense. And heavy air masses tend to blow out into lighter air masses around it.

This triggers the polar wind to blow southward, down from the Arctic. The path it takes is modified by the spinning earth which bends the prevailing winds to circle in belts around the globe. The Arctic wind first veers into the belt of the polar easter¬ lies. Farther south, in the path of the westerlies, it may be swerved westward. A forceful polar wind often blows on us from the northwest. An extra forceful polar wind may re¬fuse to be swerved by the westerlies and blast down on us from the north or northeast.