Apparent solar constant variations and their relation to the variability of atmospheric transmission

The considerations contained in the following article are all based on the large number of observations of sun radiation and atmospheric transmission collected by the Astro-physical Observatory of the Smithsonian Institution. The author has shown that there is a close correlation between the variability of transmission and the apparent variability of the solar constant as it is presented in the Volumes of the Astrophysical Observatory. The relationship is explained on the basis of theoretical deductions presented by Dr R. Lundblad (1922) and by the present author (1921) at an early date. Further results, concerning the connection between the spectral distribution of intensity of the apparent solar constant and the variations of transmission, are based on the named theory. If the variability of the apparent solar constant is reduced to a value corresponding to a constant transmission, the remaining variability seems to coincide very closely with the standard error which can be expected in radiation measurements with our most accurate pyrheliometers. A short preliminary note is added concerning the wavelength dependence of atmospheric scattering as derived from the variability of the transmission for different wavelength intervals where no selective absorption occurs.