Measurements and interpretation of the polarization of radiation emerging from the atmosphere at an altitude of 28 km over South—Western New Mexico (USA)

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Abstract
The degree of linear polarization of the upward radiation emerging from the atmosphere at an altitude of 28 km was measured over south‐western New Mexico (USA) with a balloon‐borne photoelectric polarimeter. Measurements were made in four spectral intervals (bandwidth ∼ 15 nm) centred on λλ362, 401, 501 and 599 nm. The objective was to estimate the turbidity factors of simple, homogeneous models of turbid atmospheres from a comparison of the experimental results with computed values of the polarization of the radiation emerging from the top of the model atmospheres. The computations were based on the solution of the radiative transfer problem in a homogeneous turbid atmosphere. The ‘doubling’ method was used to obtain the solution. It is found that the optimal values of the turbidity factors required to establish good agreement between theory and experiment vary directly as the phase function asymmetry factors associated with the two types of aerosols used in the models. The uncertainty in the interpretation of the polarization data due to the similar effects that the atmospheric aerosols and the unpolarized part of the radiation reflected by the ground have on the polarization of the scattered radiation is briefly discussed.