Science: Weather: Prediction and Control

An old North Woods Indian known for his accurate weather forecasts was once approached by a newspaper reporter who inquired how he could tell that the coming winter would be a cold one. Gesturing toward the cabins of his neighbors, the Indian replied: "White man make big wood pile."

The story, told frequently down in Maine, is doubtless apocryphal. But it reflects the fact that despite modern instruments and meteorological methods, weather forecasting of any kind remains at best an inexact science. Dreams of actually doing something about the weather are equally unrealistic. People pausing to rest as they shovel out from under this winter's snows or shivering in chilled homes may look longingly toward a day when science will be able to make weather to order. Was the Big Freeze really necessary? Answer: alas, yes. Despite some limited successes in making it rain on demand, most scientists believe that, for the foreseeable future, weather modification is unlikely.

Wrathful God. What is likely is that the weather, as it has done throughout history, will continue to toy with its would-be forecasters, embarrassing them with rain when they call for clear skies, drought when they predict precipitation. Indeed, the weatherman's plight will probably not change a millibar from that described by the English meteorologist Sir Napier Shaw. Wrote he: "A forecaster's heart knoweth its own bitterness, and a stranger meddleth not with its joy."

The ancients believed that weather changed at the whim of the gods, and Homer's Odyssey contains several references to storms raised against Odysseus by a wrathful Poseidon. Modern-day meteorologists have established that earth's weather stems mainly from the sun. Each day radiation equal to some 17 trillion kilowatts reaches the earth's atmosphere from the sun and warms the planet, particularly around the equatorial regions, where this radiation strikes more directly than it does at the poles.

Heated tropical air rises and flows from the equator toward the colder polar regions, while cold polar air flows toward the equator. The planet's eastward rotation skews the movement of air and causes the prevailing westerly winds that blow from North America toward Europe, and roar across the southern oceans. Topographical features, such as land masses and mountains, and uneven heating patterns further alter the air flow. The result is the assortment of high-and low-pressure regions and the winds that give the earth its weather.

Forecasting the weather has long occupied man's attention. Early farmers and sailors, whose livelihoods—and sometimes lives—depended upon the weather, learned by experience how to read the signs that frequently presaged change. Sailors realized from early days the general wisdom of the poem "Sky red in the morning/ Is a sailor's sure warning/ Sky red at night/ Is the sailor's delight." Farmers observed that dandelions and other flowers closed when a storm was approaching and had a simple way of telling the temperature from the rate at which crickets chirp: count the number of times the insect chirps in 14 seconds and then add 40.