Forest Preserve District of Cook County, Illinois
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Song of the Wind
Nature Bulletin No. 318-A   October 26, 1968
Forest Preserve District of Cook County
Richard B. Ogilvie, President
Roland F. Eisenbeis, Supt. of Conservation

SONG OF THE WIND
The wind is simply air in motion. Air has substance like wood or water, it has pressure, it can acquire heat and hold a temperature, and it can travel from place to place.... The air which affects our lives is a layer seven or eight miles thick, called the troposphere, which is next to the earth. This air has pressure (14.7 pounds per square inch at sea level) and when various factors, one of which is temperature, cause changes in this pressure, the air starts moving. We cannot see it. We can hear it. The song of the wind is the most wonderful music on earth, and at times the most terrifying in its angry moments.

Air, like water, gets hot and cold. A basic principle of the physics of air is that cold air is heavier than warm air. Air masses warmed by the sun in the tropics affect the whole earth. This tropical air, when heated by a burning sun, becomes lighter and is forced upwards by the heavier air in the regions around it. Part of it goes northward carrying heat and water vapor. These winds, going toward the north, become the "prevailing winds" for us.

The wind has no master; it knows no bounds. A great air mass can lie stagnant far to the north of us for days and weeks. It grows colder and colder and finally starts moving south, sounds like shrill trumpets marking its journey. As it travels it reacts to the force caused by the earth rotating on its axis, and then the moving air mass begins to rotate within itself in a clockwise direction. The winds, born in the air mass, blow around their stern parent, and also blow in all directions. When great air masses, one cold and dry, the other warm and moisture-laden, meet, a storm is born. Rain is also an instrument which records the music of the wind.

The song of the wind depends upon the wind's intensity. This is measured in prosaic terms of miles per hour and is described by the weather man with a series of familiar terms. You can tell the wind force by the lazy smoke drift of a mesquite fire in the desert "light", 1- 7 mph); by the uneasy movement of leaves and twigs on the ground ("gentle", 8-12 mph); by singing leaves in trees ("moderate" or "fresh" 13-18 or 19-24 mph), by whistling telephone wires ("strong", 25-38 mph); and by the sharp sounds of breaking limbs on trees and shingles torn from roofs ("gale", 39-54 mph). The furious roar of the "whole gale" (55-75 mph), and the "hurricane" (above 75 mph), which luckily so few of us experience.

The wind hums, whistles, sings or shouts as it goes about its business of planting seed, raising dust clouds, pushing storms hither and yon as the seasons change. There is the soft murmur in the wind of spring, containing idle gossip about flowers, bees, birds and gentle things. The wind of summer, reacting to the powerhouse we call the sun, is fitful and variable in its gypsy travels, and in its music reflects its temperamental moods. Winter's wind is a churlish fellow.... This wind lifts its voice in ribald and raucous song, shouting a mad ballad of the north, of glaciers, of frigid and isolated mountain peaks, of a world of ice and snow. The wind has many voices; each voice tells a different tale. There is a wind voice for every season because only with the wind, harsh or gentle, can the season sing its song. Listen to the wind and the song it sings. Knowing the wind song, you'll better understand the world in which we live.


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