Extraction of aerosol-size distributions from multispectral light extinction data

An algorithm for inverting remote sensing measurements to determine particle concentration and size distribution, proposed by Nguyen and Cox in 1989, is described and evaluated. This determination uses extinction measurements at multiple wavelengths with the solution of the Fredholm integral equation. The solution represents the second derivative of the particle-size distribution as a linear combination of orthogonal functions chosen so that the resulting solution is smooth and positive everywhere. We used this algorithm to reconstruct concentrations and size distributions for simulated and experimental measurements of light extinction caused by different test aerosols. An “information content parameter” was used to measure how well each size distribution could be reconstructed from its corresponding measurements. For a wavelength range of 340–940 nm, aerosols in the accumulation mode (300 nm < d 50 < 2500 nm) were reconstructed well. The algorithm was good at reconstructing moderately polydisperse aeroso...