SUGGESTIONS CONCERNING DR. C. G. ABBOT'S PROGRAM FOR FOUR WORLD OBSERVATORIES FOR THE OBSERVATION OF EXTRATERRESTRIAL SOLAR RADIATION

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  • 1 Davos, Switzerland
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Abstract

SYNOPSIS

The scientific and practical importance of the above program is emphasized. On account of the inadequacy of existing meteorological records, special observations, including detailed cloud records, are necessary before sites for solar observatories are finally decided upon. To obtain these cloud records and instrument, which has been employed at the Davos observatory since October, 1919, for recording the illumination of a horizontal surface by the sun and sky may be utilized.

Since, at night, the radiation to the sky varies with zenith distance but not with azimuth, it becomes possible to use for the measurements a blackened hollow sphere as an absolute black body, such as Angström's “Tulipan.” This seems to meet Abbot's objection that the absorption of blackened surfaces for wave lengths greater than 15µ is not well known, and, in consequence, measurements by instruments, like Angströs pyrgeometer contain an unknown error. Comparisons between the pyrgeometer and the Tulipan, however, show a reasonably constant ratio.

The importance of ascertaining the ozone content of the atmosphere is emphasized, and it is pointed out that photoelectric intensity measurements with cadmium cell of the spectrally decomposed ultra-violet radiation may help to solve this difficult problem.

It is suggested that for investigations in the infra-red bacteria may be used in place of photographic plates. Also, that Angströs nocturnal radiation measurements of 1913 should be repeated in optically undisturbed times. —H. H. K.

Abstract

SYNOPSIS

The scientific and practical importance of the above program is emphasized. On account of the inadequacy of existing meteorological records, special observations, including detailed cloud records, are necessary before sites for solar observatories are finally decided upon. To obtain these cloud records and instrument, which has been employed at the Davos observatory since October, 1919, for recording the illumination of a horizontal surface by the sun and sky may be utilized.

Since, at night, the radiation to the sky varies with zenith distance but not with azimuth, it becomes possible to use for the measurements a blackened hollow sphere as an absolute black body, such as Angström's “Tulipan.” This seems to meet Abbot's objection that the absorption of blackened surfaces for wave lengths greater than 15µ is not well known, and, in consequence, measurements by instruments, like Angströs pyrgeometer contain an unknown error. Comparisons between the pyrgeometer and the Tulipan, however, show a reasonably constant ratio.

The importance of ascertaining the ozone content of the atmosphere is emphasized, and it is pointed out that photoelectric intensity measurements with cadmium cell of the spectrally decomposed ultra-violet radiation may help to solve this difficult problem.

It is suggested that for investigations in the infra-red bacteria may be used in place of photographic plates. Also, that Angströs nocturnal radiation measurements of 1913 should be repeated in optically undisturbed times. —H. H. K.

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