ACP Atmospheric Chemistry and Physics ACP 1680-7324 Copernicus GmbH Göttingen, Germany 10.5194/acp-10-10017-2010 Comment on "Classification of aerosol properties derived from AERONET direct sun data" by Gobbi et al. (2007) O'Neill N. T. 1 CARTEL, Université de Sherbrooke, Sherbrooke, Québec, Canada 25 10 2010 10 20 10017 10019 This is an open-access article ditributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. This article is available from http://www.atmos-chem-phys.net/10/10017/2010/acp-10-10017-2010.html The full text article is available as a PDF file from http://www.atmos-chem-phys.net/10/10017/2010/acp-10-10017-2010.pdf

It is pointed out that the graphical, aerosol classification method of Gobbi et al. (2007) can be interpreted as a manifestation of fundamental analytical relations whose existance depends on the simple assumption that the optical effects of aerosols are essentially bimodal in nature. The families of contour lines in their "Ada" curvature space are essentially empirical and discretized illustrations of analytical parabolic forms in (α, α') space (the space formed by the continuously differentiable Angstrom exponent and its spectral derivative).

 References % vor jede Referenz Atkinson, D. B., Massoli, P., O'Neill, N. T., Quinn, P. K., Brooks, S. D., and Lefer, B.: Comparison of in situ and columnar aerosol spectral measurements during TexAQS-GoMACCS 2006: testing parameterizations for estimating aerosol fine mode properties, Atmos. Chem. Phys., 10, 51–61, doi:10.5194/acp-10-51-2010, 2010. Gobbi, G. P., Kaufman, Y. J., Koren, I., and Eck, T. F.: Classification of aerosol properties derived from AERONET direct sun data, Atmos. Chem. Phys., 7, 453–458, doi:10.5194/acp-7-453-2007, 2007. Eck, T. F., Holben, B. N., Reid, J. S., Dubovik, O., Smirnov, A., O'Neill, N. T., Slutsker, I., and Kinne, S.: The wavelength dependence of the optical depth of biomass burning, urban and desert dust aerosols, J. Geophys. Res, 104, 31333–31350, 1999. O'Neill, N. T., Eck, T. F., Holben, B. N., Smirnov, A., Dubovik, O., and Royer, A.: Bi-modal size distribution influences on the variation of Angstrom derivatives in spectral and optical depth space, J. Geophys. Res., 106, 9787–9806, 2001a. O'Neill, N. T., Dubovik, O., and Eck, T. F.: A modified Angstrom coefficient for the characterization of sub-micron aerosols, App. Opt., 40(15), 2368–2374, 2001b. O'Neill, N. T., Eck, T. F., Smirnov, A., Holben, B. N., and Thulasiraman, S.: Spectral discrimination of coarse and fine mode optical depth, J. Geophys. Res., 108(D17), 4559–4573, doi:10.1029/2002JD002975, 2003. O'Neill, N. T., Thulasiraman, S., Eck, T. F., and Reid, J. S.: Robust optical features of fine mode size distributions; application to the Québec smoke event of 2002, J. Geophys. Res., 110(D11), D11207, doi:10.1029/2004JD005414, 2005.