Kathy Jackson, age 10, of Eureks, Kansas, for her question:
What causes a whirlwind?
On a hot summer's day the merry little whirlwinds dance over the dry deserts and the dusty prairies. You might mistake them for small relatives of the angry tornado. Both are spinning, spiraling winds, stirring up dust and debris. However, the angry tornado dips down from a turbulent cloud. The merry whirlwind reaches up from the ground. What's more, the torn'‑do is the fiercest storm on earth. The whirlwind is rarely, if ever, strong enough to do any damage.
The summer sun heats up the surface of the dry, dusty ground. The ground heats the layer of air th^t touches it. ;ibove this warm lower layer the air may be cooler, quite a lot cooler. This difference in temperature sets eddies and. air currents in motion.
The atmosphere, it seems, does not like to be patchy. But the ground is forever warming a patch of air hero and leaving a patch of cool air there. To oven things up the patches of cool, dense air tend to flow in towards patches of warm, light air. This moving air is the wind,
The air does not get its warmth from the sun. Otherwise the top of the atmosphere would be the hottest, Snow would melt on the mountain tops and remain on the lower ground. Instead of this, sunshine passes down through the air, giving up little or none of its boat. It saves heat to pour on the face of the earth, land end sea. The surface of the earth becomes warm end some of its heat rises to warm the air which touches it.
Sometimes the layer of air above the warm ground level remains cool. This is what happens when a whirlwind is born. The warm air below expands, rising end roeching up into the cool air above. A finger of light, warm air pokes a hole into the cool, denser air. The air surrounding is pulled inwards and upwards. Then the column of inflowing rising air starts to spin and a whirlwind is born.
The merry little dancer can spin in either direction, from the right or from to left. But the column of air always starts at ground level and reaches upwards. Sometimes a dozen or more dusty little whirlers can be seen dancing over the desert tar prairie. Some stay in one spot, some take a walk waltzing along in a cloud of dust wherever the fancy moves them.
All this spinning andl whirling stirs up the air. Warm air mixes with the cool air above and becomes cooler. A host of dancing whirlwinds actually make the lower air cooler than it would be otherwise. However, the little spinners are too small to lower the temperature to any great degree.
Most whirlwinds prefer to dance in the wide open spaces. But, once in a while, one is born among trees or buildings. Usually it stirs up no more than a playful breeze. But a real grandpa; whirlwind can whip twists off a tree, shingles off a roof and bang the shutters.