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3 October 1997 Influence of aerosol on the degree of linear polarization of skylight in the O2-A band
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We have investigated the influence of atmospheric aerosol on the degree of linear polarization P of diffusely transmitted radiation within the O2-A band, between 755 and 775 nm. In this wavelength interval, the molecular absorption optical thickness of the atmosphere ranges approximately from 10-3 to 2 X 102, whereas the atmospheric molecular scattering optical thickness is an small as 0.025. Radiative transfer calculations have been performed for a terrestrial-like atmosphere to calculate P of the transmitted radiation as a function of the atmospheric molecular absorption optical thickness. Results are presented both for a clear atmosphere and for aerosol loaded atmospheres. It is shown that for small absorption optical thicknesses P is mainly determined by first order scattering by particles in the lower atmospheric layers. For absorption optical thicknesses larger than about 10, the degree of linear polarization of the transmitted radiation is dominated by P of the radiation that has taken the shortest optical path through the atmosphere. For the zenith sky radiation, P is then mainly determined by single scattering in the upper atmospheric layers. For radiation from other directions, P then largely results from two scatterings: the first one by particles in the upper atmospheric layers in the nadir direction, and the second one by particles in the lower layers. It is concluded that information on tropospheric aerosol particles can be derived from polarization measurements of the diffusely transmitted radiation outside the O2-A absorption band. In the strongest parts of the band, zenith sky polarization measurements contain information on the stratospheric aerosol particles.
© (1997) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Daphne M. Stam, Johan F. de Haan, Joop W. Hovenier, and Piet Stammes "Influence of aerosol on the degree of linear polarization of skylight in the O2-A band", Proc. SPIE 3121, Polarization: Measurement, Analysis, and Remote Sensing, (3 October 1997);

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