Sky radiation, polarization and twilight radiation in Greenland

A) The measurements of the spectral radiances in the solar almucantar (scattering function) and the degree of polarization of the skylight in Greenland indicate the following: 1) The air near the surface of the ice cap of Northern Greenland is very pure. 2) The sky radiance however is different from the pure molecular (Rayleigh) atmosphere, the measured scattering function does not followRayleigh's law. 3) On the other hand the measured scattering functions cannot be explained satisfactoryly by scattering on the aerosols which have been measured near the surface. 4) Therefore the presence of a few particles per cm3 with radii in the range 0.10≤r≤1μ in heigher atmospheric layers has to be po…

The Elliptical Polarization of Light Scattered by a Volume of Atmospheric Air

The scattering of linearly polarized light by aerosol particles produces partly polarized light whose ellipticity is theoretically and experimentally investigated for the specific case of a continental atmospheric aerosol in a volume of air. With the Mie theory and under the assumption of various aerosol size-distribution models, the ellipticity has been computed as a function of the scattering angle for various wavelengths. The computations have been based upon complex indices of refraction: M = 1.5-0.0i, M = 1.5-0.0li, M = 1.5-0.li, M = 1.44-0.0i, M = 1.4-0.0i, M = 1.33-0.0i. The comparison between computed and measured values for the wavelengths of lambda = 0.45 micro to lambda = 0.65 mi…

The Influence of the Size of the Sun on the Sky Light Distribution

Calculations and measurements of the spectral radiance of the solar aureole

The application of the theory of primary scattering to describe and interpret the spectral distribution of the sky radiance is discussed. It is shown that within the solar aureole the influence of the scattering of higher order can be neglected. Theoretical calculations of the spectral distribution of the sky radiance, carried out by Bullrich et al . (1965) based on an exponential aerosol size distribution with an upper limiting particle radius r = 10 ?, have been extended to r = 150 ?. The detailed study of the influence of these “giant” particles revealed that aerosol particles of r >30 ? have no effect on the sky radiation any more. Representative measurements taken at Mainz, Germany, at…

Solar radiation extinction, sky radiation, sky light polarization and aerosol particle total number and size distribution on the Island Maui (Hawaii)

During April 1964 and from August through September 1965 measurements have been performed on the Maui Island, Hawaii. The results can be summarized as follows: a) the spectral extinction coefficient has a diurnal variation. The greatest value is found during noon. Its wavelength dependency shows an ‘anomalous extinction’, the maximum of extinction is to be found at 0.55 μ (Figures 1–3). b) the spectral radiance distribution of the total sky indicates the tendency that the aerosol size distribution does not follow a continuous power law. The exponent for small particles seems to bev*1 μ (Figure 8). d) the distribution of spectral degree of sky light polarization shows two maxima of polarizat…