Atmospheric Chemistry and Physics Discussions www.atmos-chem-phys-discuss.net 1680-7367 1680-7375 8 1 2008 10.5194/acpd-8-3895-2008 http://www.atmos-chem-phys-discuss.net/8/3895/2008/ http://www.atmos-chem-phys-discuss.net/8/3895/2008/acpd-8-3895-2008.html http://www.atmos-chem-phys-discuss.net/8/3895/2008/acpd-8-3895-2008.pdf 3895 3919 2008-02-26 Validation of UV-visible aerosol optical thickness retrieved from spectroradiometer measurements C. Brogniez colette.brogniez@univ-lille1.fr V. Buchard F. Auriol LOA/CNRS, Université des Sciences et Technologies de Lille, France Global and diffuse UV-visible solar irradiances are routinely measured since 2003 with a spectroradiometer operated by the Laboratoire d'Optique Atmosphérique (LOA) located in Villeneuve d'Ascq, France. The analysis of the direct irradiance derived by cloudless conditions enables retrieving the aerosol optical thickness (AOT) spectrum in the 330–450 nm range. The site hosts also sunphotometers from the AERONET/PHOTONS network performing routinely measurements of the AOT at several wavelengths. On one hand, comparisons between the spectroradiometer and the sunphotometer AOT at 440 nm as well as, when available, at 340 and 380 nm, show good agreement. On the other hand, the AOT's spectral variations have been compared using the Angström exponents derived from AOT data at 340 and 440 nm for both instruments. The comparisons show that this parameter is difficult to retrieve accurately due to the small wavelength range and due to the weak AOT values. Thus, AOT derived at wavelengths outside the spectroradiometer range by means of an extrapolation using the Angström parameter would be of poor value, whereas, spectroradiometer's spectral AOT could be used for direct validation of other AOT, such as those provided by satellite instruments. Arola, A. and Koskela, T.: On the sources of bias in aerosol optical depth retrieval in the UV range, J. Geophys. Res., 109, doi:10.1029/2003JD004375, 2004. Bais, A., Kazantzidis, A., Kazadzis, S., Balis, D., Zerefos, C., and Meleti, C.: Deriving an effective aerosol single scattering albedo from spectral surface UV irradiance measurements, Atmos. Environ., 39, 1093–1102, 2005. Bernhard, G. and Seckmeyer, G.: Uncertainty of measurements of spectral solar UV irradiance, J. Geophys. Res., 104, 14 321–14 345, 1999. Bodhaine, B. A., Wood, N. B., Dutton, E. G., and Slusser, J. R.: On Rayleigh Optical Depth Calculations, J. Atmos. Oceanic Technol., 16, 1854–1861, 1999. Burrows, J. P., Dehn, A., Deters, B., Himmelmann, S., Richter, A., Voigt, S., and Orphal, J.: Atmospheric Remote-Sensing Reference Data from GOME: 1. Temperature-Dependent Absorption Cross Sections of NO₂ in the 231–794 nm Range, J. Quant. Spectrosc. Radiat. Transfer, 60, 1025–1031, 1998. Cheymol, A., De Backer, H., Josefsson, W., and Stubi, R.: Comparison and validation of the aerosol optical depth obtained with the Langley plot method in the UV-B from Brewer ozone Spectrophotometer measurements, J. Geophys. Res., 111, D16202, doi:10.1029/2006JD007131, 2006. de La Casinière, A., Cachorro, V., Smolskaia, I., Lenoble, J., Sorribas, M., Hou\"et, M., Massot, O., Anton, M., and Vilaplana, J. M.: Comparative measurements of total ozone amount and aerosol optical depth during a campaign at El Arenosillo, Huelva, Spain, Ann. Geophys., 23, 3399–3406, 2005. Dubovik, O., Holben, B., Eck, T. F., Smirnov, A., Kaufman, Y. J., King, M. D., Tanré, D., and Slutsker, I.: Variability of absorption and optical properties of key aserosol types observed in worldwide locations, J. Atmos. Sci., 59, 590–608, 2002. Eck, T. F., Holben, B. N., Reid, J. S., Dubovik, O., Smirnov, A., O'Neill, N. T., Slutsker, I., and Kinne, S.: Wavelength dependence of the optical depth of biomass burning, urban, and desert dust aerosols, J. Geophys. Res., 104(D24), 31 333–31 349, 1999. Gröbner, J. and Meleti, C.: Aerosol optical depth in the UVB and visible wavelength range from Brewer spectrophotometer direct irradiance measurements: 1991–2002, J. Geophys. Res., 109, D09202, doi: 10.1029/2003JD004409, 2004. Hamonou, E., Chazette, P., Balis, D., Dulac, F., Schneider, X., Galani, E., Ancellet, G., and Papayannis, A.: Characterization of the vertical structure of Saharan dust export to the Mediterranean basin, J. Geophys. Res., 104(D18), 22 257–22 270, 1999. Hou\"et, M.: Spectroradiométrie du rayonnement Solaire UV au sol: Améliorations apportées à l'instrumentation et au traitement des mesures, Analyse pour l'évaluation du contenu atmosphérique en ozone et en aérosols, Ph. D. thesis, Univ. of Lille, France, 2003. Hou\"et, M. and Brogniez, C.: Ozone column retrieval from solar UV irradiance measurements at ground level: sensitivity tests and uncertainty estimation, J. Geophys. Res., 109, D15302, doi: 10.1029/2004JD004703, 2004. Holben, B. N., Eck, T. F., Slutsker, I., Tanré, D., Buis, J. P., Setzer, A., Vermote, E., Reagan, J. A., Kaufman, Y. J., Nakajima, T., Lavenu, F., Jankowiak I., and Smirnov A., AERONET – A federated instrument network and data archive for aerosol characterization, Rem. Sens. Environ., 66, 1–6, 1998. Forster, P., Ramaswamy, V., Artaxo, P., et al.: Changes in Atmospheric Constituents and in Radiative Forcing, in: Climate Change 2007: The Physical Science Basis, Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, edited by: Solomon, S., Qin, D., Manning, M., Chen, Z., Marquis, M., Averyt, K. B., Tignor, M., and Miller, H. L., Cambridge University Press, Cambridge, UK and New York, NY, USA, IPCC report, (http://www.ipcc.ch/ipccreports/ar4-syr.htm), 2007. Kazadzis, S., Bais, A., Kouremeti, N., Gerasopoulos, E., Garane, K., Blumthaler, M., Schallhart, B., and Cede, A.: Direct spectral measurements with a Brewer spectroradiometer: absolute calibration and aerosol optical depth retrieval, Appl. Opt., 44(9), 1681–1690, 2005. Key, J.: Streamer user's guide, Technical report 96–01, Department of Geography, Boston University, 1999. Krotkov, N., Bhartia, P. K., Herman, J., Slusser J., Scott, G., Labow, G., Vasilkov, A. P., Eck, T. F., Dubovik, O., Holben, B. N.: Aerosol ultraviolet absorption experiment (2002 to 2004), part 2: absorption optical thickness, refractive index, and single scattering albedo, Optical Engineering, 44(4). doi: 10.1117/1.1886819, 2005. Orphal, J. and Chance, K.: Ultraviolet and visible absorption cross-sections for HITRAN, J. Quant. Spectrosc. Radiat. Transfer, 82, 491–504, 2003. Paur, R. J. and Bass, A. M.: The ultraviolet cross sections of ozone, II, Results and temperature dependence, in: "Atmospheric Ozone, Proceedings of the Quadriennal Ozone Symposium", edited by: Zerefos, C. and Ghazi, A., 611–616, 1985. Petters, J. L., Saxena, V. K., Slusser, J. R., Wenny, B. N., and Madronich, S.: Aerosol single scattering albedo retrieved from measurements of surface UV irradiance and a radiative transfer model, J. Geophys. Res., 108(D9), 4288, doi:10.1029/2002JD002360, 2003. Slaper, H., Reinen, H., Blumthaler, M., Huber, M., and Kuik, F.: Comparing ground-level spectrally resolved solar UV measurements using various instruments: a technique resolving effects of wavelength shift and slit width, Geophys. Res. Lett., 22(20), 2721–2724, 1995. Thuillier, G., Hersé, M., Labs, D., Foujols, T., Peetermans, W., Gillotay, D., Simon, P.C., and Mandel, H.: The solar spectral irradiance from 200 to 2400 nm as measured by the SOLSPEC spectrometer from the ATLAS and EURECA missions, Solar Physics, 214, 1–22, 2003. Wenny, B. N., Saxena, V. K., and Frederick, J. E.: Aerosol optical depth measurements and their impact on surface levels of ultraviolet-B radiation, J. Geophys. Res, 106(D15), 17 311–17 319, 2001.