C. G. Abbot

The Value of the Solar Constant of Radiation

We have made hitherto nearly 1000 determinations of the intensity of solar radiation outside the atmosphere at mean solar distance, termed the solar constant of radiation. The mean value found is 1.93 calories per square centimeter per minute. Langleys spectro-bolometric method was employed. This consists in determining the distribution of the energy in the solar spectrum at different solar zenith distances, and thereby computing coefficients of atmospheric transmission suitable to determine the energy curve outside the atmosphere. The bolometric measurements are reduced in terms of standard 15° calories per square centimeter per minute by the aid of comparisons made each day of observation with standardized pyrheliometers. Observations have been made at Washington (sea level); Bassour, Algeria (1160 meters); Mount Wilson, California (1730 meters); and Mount Whitney, California (4420) meters. They have continued during all the years 1903 to 1914. Great changes from day to day and from place to place in temperature, in barometric pressure, in humidity, in haziness, while of course greatly affecting measurements of intensity at the stations, and of atmospheric transparency computed, nevertheless have not produced differences of the solar constant values. This seems to us to be strong evidence of the soundness of the method. In the second place it has been shown by Fowle that the atmospheric transmission coefficients obtained at Mount Wilson fit well with Lord Rayleighs theory of atmospheric scattering, except for those regions of spectrum where numerous atmospheric lines and bands of true absorp-

Weather and solar variation

Abstract As solar radiation and the weather appear to be affected by identical periods of variation, it is therefore likely that weather changes are produced by solar variation, and can be predicted when the periods are known. Forecasts for precipitation and temperature at St. Louis and Peoria are compared graphically with actual weather data, based on 5-month smoothed running means and extending from 1854 to 1939, as evidence of the authors thesis.

Utilizing heat from the sun

Modern development of aluminum products and vacuum devices makes feasible and economically practical the wholesale production of solar-heat appliances for various purposes, according to an authority on solar radiation who has been experimenting with such appliances for 20 years.

Detailed procedure used in Abbot's method of long-range weather forecasting

Abstract As a result of 30 years of daily observations of the solar constant, the author discovered a numerous family of regular periodic variations of solar radiation, all integrally related to the master period of 273 months. Exactly the same family of variations was found in long-interval precipitation and temperature records, hidden to cursory search by phase changes due to various atmospheric influences. In solar variation the periods have ranges of only 0.05 to 0.21 per cent of the solar constant, whereas in precipitation they range from 5 to 25 per cent of normal, and in temperature up to 5° F. This paper describes in detail a method of forecasting author has evolved from this discovery. His method can be used for forecasts up to fifty years in advance, but yields only general features, such as monthly or seasonal effects, not weekly or daily changes. With the aid of Professor C. Wexler of Arizona State College, a forecast was made for Natural Bridge, Arizona, from 1950 to 1967. The results and a comparison with the event to 1957 are given in a graph.

Solar Variation and the Weather

NEARLY a century ago three pioneers, Sir John Herschel, Pouillet, and Forbes, laid the foundations of the measurement of solar radiation. Each devised an instrument for measuring the heating effect of the solar rays and used it diligently. Pouillet and Forbes availed themselves of the law of extinction of light, which had been independently discovered about 1760 by Bouguer and Lambert, to calculate the intensity of the solar rays, as they would be outside our atmosphere. Forbess researches in the Alps proved that this law is not strictly applicable to the suns rays as a whole, and he was led to believe that the value of the so-called solar constant of radiation was as high as 2.85 calories per sq. cm. per mm. Pouillets value, based on the assumed validity of the Bouguer-Lambert law, was 1.76 calories.