Sun Rays and Weather

Everybody talks about the weather but nobody does anything about it, complained Mark Twain. Last week, however, somebody did. Dr. Charles Greeley Abbot, grey, 72-year-old Secretary of the Smithsonian Institution, announced the most important advance in weather forecasting since 1909.*

Dr. Abbot had developed a method of long-range prediction by measuring variations in the amount of heat the earth gets from the sun. His system works so well that last year he forecast almost to the drop how much rain would fall and which days would be rainy in Washington, D.C.

Scientists in general have given surprisingly little study to the effects of the sun on the weather. But Astrophysicist Abbot has been watching solar radiation with heliotrope devotion for 49 years. Twenty-five years ago he began to take daily recordings of solar heat. The Smithsonian set up delicate measuring instruments on three mountaintops in desert areas which averaged 300 cloudless days a year--Table Mountain, Calif., Burro Mountain, N. Mex. and Mt. Montezuma, Chile.

The heat the earth normally gets from the sun is the equivalent of 250 trillion horsepower. But Dr. Abbot found that on any given day solar heat might vary as much as 5% from normal. One reason: sunspots, which throw out great conical sprays of electric particles that interfere with solar rays. When Dr. Abbot compared changes in solar heat with changes in the weather, he discovered some remarkable parallels: a rise in solar activity was almost invariably followed (usually in 14 to 17 days) by a fall in earthly temperatures, and vice versa. A solar change of less than 1% sometimes caused a 10DEG change in temperature. Solar changes also seemed to affect the barometer according to a definite pattern. Pursuing these rhythms further, he learned that solar heat and weather alike had clearly marked cycles, ranging from eight months to 22 3/4 years, i.e., certain minor weather changes (after allowing for seasons and local conditions) tend to repeat themselves at eight-month intervals, and major changes in 22 3/4 years.

Monkish Learning. Still not sure that his theory was proved, Dr. Abbot learned that Jesuit monks at an observatory in Spain had photographed, every day from 1910 to 1937, certain calcium clouds on the sun's surface. Dr. Abbot compared measurements of fluctuation in the area of these clouds with his own measurements of solar heat and weather. To his great delight, all three showed almost exactly the same pattern of ups & downs.

Now confident that he had a workable system, Dr. Abbot told the Weather BuReau last March that on 175 specified days during 1943 it was likely to rain in Washington, and that rainfall on those days would be 166% of normal. Actual figure at year's end: 158%. He also correctly predicted the three days of heaviest Washington rainfall in January and February this year. Once, consulted by an Army engineer, he predicted that during a three-month period rainfall in the Tennessee Valley would be 84 to 87% of normal.

Actual rainfall: 87%. Looking far ahead, Dr. Abbot forecasts great droughts in the Northwest in 1975 and 2020 which will seriously lower the level of the Great Lakes.

Dr. Abbot's forecasts are still far from infallible, but he believes that by a proper combination of observations on solar heat, air-mass movements and local disturbances, it should be possible to predict weather at least two weeks ahead with almost perfect accuracy.

* Date of the "air-mass theory", now the basis of miltary forecasts.

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