Scattering matrices of mineral aerosol particles at 441.6 nm and 632.8 nm

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Read Full Article Cited by JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 106, NO. D15, PAGES 17,375–17,401, 2001 Scattering matrices of mineral aerosol particles at 441.6 nm and 632.8 nm H. Volten Department of Physics and Astronomy, Free University, Amsterdam, Netherlands O. Muñoz Department of Physics and Astronomy, Free University, Amsterdam, Netherlands E. Rol Department of Physics and Astronomy, Free University, Amsterdam, Netherlands J. F. de Haan Department of Physics and Astronomy, Free University, Amsterdam, Netherlands W. Vassen Department of Physics and Astronomy, Free University, Amsterdam, Netherlands J. W. Hovenier Department of Physics and Astronomy, Free University, Amsterdam, Netherlands K. Muinonen Observatory, University of Helsinki, Finland T. Nousiainen Department of Meteorology, University of Helsinki, Finland Abstract We present measured scattering matrices as functions of the scattering angle in the range 5°-173° and at wavelengths of 441.6 nm and 632.8 nm for seven distinct irregularly shaped mineral aerosol samples with properties representative of mineral aerosols present in the Earth's atmosphere. The aerosol samples, i.e., feldspar, red clay, quartz, loess, Pinatubo and Lokon volcanic ash, and Sahara sand, represent a wide variety of particle size (typical diameters between 0.1 and 100 μm) and composition (mainly silicates). We investigate the effects of differences in size and complex refractive index on the light-scattering properties of these irregular particles. In particular, we find that the measured scattering matrix elements when plotted as functions of the scattering angle are confined to rather limited domains. This similarity in scattering behavior justifies the construction of an average aerosol scattering matrix as a function of scattering angle to facilitate, for example, the use of our results for the interpretation of remote sensing data. We show that results of ray-optics calculations, using Gaussian random shapes, are able to describe the experimental data well when taking into account the high irregularity in shape of the aerosols, even when these aerosols are rather small. Using the results of ray-optics calculations, we interpret the differences found between the measured aerosol scattering matrices in terms of differences in complex refractive index and particle size relative to the wavelength. The importance of our results for studies of astronomical objects, such as planets, comets, asteroids, and circumstellar dust shells is discussed. Received 21 July 2000; accepted 26 January 2001. Read Full Article Cited by Citation: Volten, H., O. Muñoz, E. Rol, J. F. de Haan, W. Vassen, J. W. Hovenier, K. Muinonen, and T. Nousiainen (2001), Scattering matrices of mineral aerosol particles at 441.6 nm and 632.8 nm, J. Geophys. Res., 106(D15), 17,375–17,401. Copyright 2001 by the American Geophysical Union.

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