Aerosol Size Distributions from Genetic Inversion of Polar Nephelometer Data*

It is shown that genetic inversions can be used to recover lognormal aerosol size distributions from multiangle optical scattering cross-section data measured by a polar nephelometer at a wavelength of 0.532 μm. The inversions can also be used to recover the absolute calibration factor of the polar nephelometer. The method is demonstrated by applying it to polar nephelometer data measured during the Shoreline Environment Aerosol Study (SEAS) at Bellows Beach on the island of Oahu, Hawaii. Also, the inverted size distributions are compared with those inferred from direct measurements by particle sizers during SEAS. At 0.532 μm, the polar nephelometer data are dominated by the effect of coarse-mode hydrated sea salt. Although the inversion was unable to place constraints on the accumulation-mode size distribution, the modeled size distribution provides a good description of optical scattering at wavelengths of 0.532 μm and above.