Sandy Albright, age 11, of Spokane, Wash.
What exactly the troposphere?
The troposphere blew into Andy’s column a few weeks ago. It is the weathery region of the atmosphere and if we knew all of its tricks we could tell for sure when and where and how much it will rain. But the troposphere is vast and tricky, Even with a world‑wide network of weather watchers, plus a few weather satellites on high, the best forecaster has been known to make mistakes.
The troposphere, of course, is made of gases and gases must obey certain laws. One law says that a gas must spread out evenly through all available space. You might suspect that there is no limit to the space available to the troposphere, but this is not so. TIts home is huge, but nevertheless it has a floor and a roof. Its floor is the globe, where it sits on land and sea, Its roof is a layer of calm air called the tropopause which varies from about five miles over the equator to about 11 miles over the poles. .
In this space, enveloping the whole world, the filmy troposphere tries to keep its gases evenly distributed. Masses of dense, heavy air rush in to fill out regions of light, thin air, Dry air drinks up moisture and over‑saturated air drops its moisture as rain and snow. But the .job is never done, for the sun and the earth conspire to turn it into a patchwork quilt of dense air and light air, damp air and dry.
The radiant energy of the sun passes straight through the atmosphere, giving up little or none of its heat until it reaches the earth, There some of this energy is turned to heat by the land and the face of the sea, The air gets its heat from the land and sea below it. And the heat it gets from below is changeable, as changeable as the weather. It changes with the seasons, with night and day, with the tropics and polar regions.
It even changes with land and sea. Warm air tends to expand and become light. Cool air tends to become dense and heavy. The trade winds are simply masses of denser air flowing in to fill the region of light, rising air above the equator, A mass of dense, cold air over northern Canada may flow down to Join with warmer air and carry a storm clear across the continent.
Warm air over the ocean drinks up water vapor. But there are rules about this too. The air can hold so much vapor and no more, depending upon its temperature. If the warm, damp air meets a. mkss of cold air, some of its vapor mist be dumped, tt may turn Into clouds or fall as rain. In all this, the gases of the troposphere are merely trying to spread themselves evenly through the available space. This never ending job results in the ever changing weather which blankets our globe.
The troposphere is but a thin layer of the total atmosphere. Above it the air reaches perhaps a thousand miles, getting thinner and thinner all the time until it finally peters out somewhere far above our heads. Most of this air, however, is down in the lower troposphere. Half of the total atmosphere is pressed into the lower level, about three and a half miles deep. Three quarters of the atmosphere is in the troposphere.