Jeanne Smith, age 15, .of Spokane, Wash., for her question:

WHAT CAUSES WIND?

Wind is caused by the uneven heating of the atmosphere by energy from the sun. The atmosphere is the air around the earth.

Air above hot areas expands and rises. Air from cooler areas then flows in to take the place of the heated air. This process is called circulation.

When there is general circulation over large sections of the earth's surface, we have prevailing winds. There are no prevailing winds near the equator or up to about 700 miles on either side of it because the air rises there instead of moving across the earth. Secondary circulation is the motion of air around relatively small regions of high and low pressure in the atmosphere.