SCATTERING FUNCTION AND POLARIZATION OF SKYLIGHT IN THE ULTRAVIOLET TO THE NEAR INFRARED REGION, WITH HAZE OF SCATTERING TYPE 2

Abstract

Measurements of the scattering-phase function and of the polarization of skylight in rather strong haze of turbidity type 2, in the wavelength range from 0.38 to 1.76 ?, have been made at Mainz, Germany. As already found earlier, the relative scattering-phase function is independent of wavelength in the visible part of the spectrum. For the increased slope of the phase function from 3 to 30 deg scattering angle in the infrared, however, a sufficient explanation cannot be given. The polarization was investigated in the sun's vertical, at solar distances of 30, 40, 60, 90 and 120 deg. Theoretical considerations suggest that the observed mean polarization at 90 deg is consistent with a polarization of about 41 per cent independent of wavelength, of haze alone. The comparison of scattering function and polarization measurements of skylight, and of the industrially contaminated air near the ground as measured by searchlights, suggests different size distribution of natural and anthropogenous air pollution.