Shirley Keith, age 13, of Keithville, Louisiana, for her question:
How can they say the sun makes all our weather?
The sun, as everybody knows, sheds golden light and radiant warmth upon the earth. The world wide weather includes howling hurricanes and blustering blizzards, raging winds and scowling black rain clouds. It seems unlikely that these items can be blamed on the beaming sun.
It seems unlikely, but every weather event from a foggy drizzle to a towering thunderhead can indeed be blamed upon the sun. The sun and the spinning earth together cause the turbulent world wide picture of weather and climate. If the earth did not rotate on its axis, maybe just maybe the sun would beam blissfully down on half the globe, with no interrupting winds and storms. But the earth does rotate on its axis, once every day. It also orbits around the sun every year and it happens to be tilted on its axis as it goes.
All these complex motions of the earth conspire together to upset the filmy air of the atmosphere. Sunbeams on their way down to the ground give up little or no warmth to the air. The atmosphere gets its warmth from the land and sea areas it touches. The lowest layer gets most of this warmth and gives small helpings to the layers above it.
The air, of course, is a mixture of gases and warmth makes all gases spring into action. Their separate molecules use extra heat energy to move faster and spread farther apart. Warm air expands and becomes lighter. Since the dizzy earth is always moving, the beaming sun can warm only certain patches of the surface at a time. The air above these favored patches becomes warm. Here, the warm air above becomes lighter and thinner. The air above cold regions gets less heat. Its gaseous molecules slow down and crowd together. Cold air gets denser and heavier and tends to blow outward into masses of lighter air.
The strongest winds blow out from the polar regions, where the air gets cold and heavy, to the equator where daily doses of sunshine create masses of warm, light air. Along the way, the spinning earth twists, or deflects, these basic winds to form the prevailing winds that girdle around the globe. Meantime other factors are added to stir up the restless atmosphere. In certain areas, the sun's warmth evaporates water from the seas and this vapor is added to the air. The atmosphere tries hard to keep its warm and cool, moist and dry air masses mixed evenly together. But the whirling earth and the beaming sun work together to keep it in a restless state of confusion. And all this turbulence creates the changing events of our weather.
The basic world wide picture begins with the cold, heavy polar winds that blow to merge with the light warm air above the equator. Local events add smaller disturbances to the picture. Land and sea breezes change as the sun's warmth changes over land and sea. The cooler air aloft condenses moisture from the seas to form clouds. Different air masses tangle in weathery warfare and planetary winds blow these stormy pockets around the globe. All these events are caused by the sun and the whirling globe.