In situ aerosol characterization at Cape Verde Part 2: Parametrization of relative humidity- and wavelength-dependent aerosol optical properties

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Schladitz, Alexander ; Müller, Thomas ; Nordmann, Stephan ; Tesche, Matthias ; Groß, Silke ; Freudenthaler, Volker ; Gasteiger, Josef ; Wiedensohler, Alfred (2011)

An observation-based numerical study of humidity-dependent aerosol optical properties of mixed marine and Saharan mineral dust aerosol is presented. An aerosol model was developed based on measured optical and microphysical properties to describe the marine and Saharan dust aerosol at Cape Verde. A wavelength-dependent optical equivalent imaginary part of the refractive index and a scattering non-sphericity factor for Saharan dust were derived. Simulations of humidity effects on optical properties by the aerosol model were validated with relative measurements of the extinction coefficient at ambient conditions. Parametrizations were derived to describe the humidity dependence of the extinction, scattering, and absorption coefficients as well as the asymmetry parameter and single scattering albedo. For wavelengths (300–950 nm) and dry dust volume fractions (0–1), aerosol optical properties as a function of relative humidity (RH = 0–90%) can be calculated from tabulated parameters. For instance, at a wavelength of 550 nm, a volume fraction of 0.5 of dust on the total particle volume (dry conditions) and a RH of 90%, the enhancements for the scattering, extinction and absorption coefficients are 2.55, 2.46 and 1.04, respectively, while the enhancements for the asymmetry parameter and single scattering albedo are 1.11 and 1.04.DOI: 10.1111/j.1600-0889.2011.00568.x
  • References (79)
    79 references, page 1 of 8

    Anderson, T. L., Covert, D. S., Marshall, S. F., Laucks, M. L., Charlson, R. J. and co-authors. 1996. Performance characteristics of a highsensitivity, three-wavelength, total scatter/backscatter nephelometer. J. Atmos. Oceanic Technol. 13, 967-986.

    Anderson, T. L., Masonis, S. J., Covert, D. S., Ahlquist, N. C., Howell, S. G. and co-authors. 2003. Variability of aerosol optical properties derived from in situ aircraft measurements during ACE-Asia. J. Geophys. Res. 108, 8647.

    Anderson, T. L. and Ogren, J. A. 1998. Determining Aerosol radiative properties using the TSI 3563 integrating nephelometer. Aerosol Sci. Technol. 29, 57-69.

    Andreae, M. O. 1995. Climatic effects of changing atmospheric aerosol levels. In: Future Climates of the World: A Modelling Perspective (ed. A. Henderson-Sellers). Elsevier, Amsterdam, 347-398.

    Andreae, M. O. and Gelencse´r, A. 2006. Black carbon or brown carbon? The nature of light-absorbing carbonaceous aerosols. Atmos. Chem. Phys. 6, 3131-3148.

    Ansmann, A., Petzold, A., Kandler, K., Tegen, I., Wendisch, M. and coauthors. 2011. Saharan Mineral Dust Experiments SAMUM-1 and SAMUM-2: what have we learned? Tellus 63B, this issue.

    Bergstrom, R. W., Russell, P. B. and Hignett, P. 2002. Wavelength dependence of the absorption of black carbon particles: predictions and results from the TARFOX experiment and implications for the aerosol single scattering albedo. J. Atmos. Sci. 59, 567-577.

    Bi, L., Yang, P., Kattawar, G. W. and Kahn, R. 2010. Modeling optical properties of mineral aerosol particles by using nonsymmetric hexahedra. Appl. Opt. 49, 334-342.

    Bohren, C. F. and Huffman, D. R. 1983. Absorption and Scattering of Light by Small Particles. New York, John Wiley & Sons, Inc.

    Bond, T. C., Anderson, T. L. and Campbell, D. 1999. Calibration and intercomparison of filter-based measurements of visible light absorption by aerosols. Aerosol Sci. Technol. 30, 582-600.

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