Degree of Interdependence among Atmospheric Optical Thicknesses in Spectral Bands between 0.36–2.4 μm

Robert S. Fraser Goddard Space Flight Center, NASA, Greenbelt, Md. 20771

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Abstract

The degree of dependence among the atmospheric optical thicknesses that are measured in nonselective absorption bands is studied. The observations were made previously in many spectral bands within the range 0.36–2.4 μm from near sea level in two continents where urban and industrial pollutions were weak. The sample covariance matrices and corresponding eigenvalues and eigenvectors are computed. The two highest eigenvalues account for 90% of the total variance in 10 spectral bands within the range 0.4–1.6 μm. The linear regression of the optical thickness on the total precipitable water vapor is computed to determine the attenuation coefficient that is associated with water vapor. This coefficient decreases rapidly with wave-length as λ−3.7 in the visible spectrum and indicates that numerous water particles of radius 0.03–0.06 μm cause the attenuation.

Abstract

The degree of dependence among the atmospheric optical thicknesses that are measured in nonselective absorption bands is studied. The observations were made previously in many spectral bands within the range 0.36–2.4 μm from near sea level in two continents where urban and industrial pollutions were weak. The sample covariance matrices and corresponding eigenvalues and eigenvectors are computed. The two highest eigenvalues account for 90% of the total variance in 10 spectral bands within the range 0.4–1.6 μm. The linear regression of the optical thickness on the total precipitable water vapor is computed to determine the attenuation coefficient that is associated with water vapor. This coefficient decreases rapidly with wave-length as λ−3.7 in the visible spectrum and indicates that numerous water particles of radius 0.03–0.06 μm cause the attenuation.

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