Atmospheric Chemistry and Physics www.atmos-chem-phys.net 1680-7316 1680-7324 8 18 2008 10.5194/acp-8-5615-2008 http://www.atmos-chem-phys.net/8/5615/2008/ http://www.atmos-chem-phys.net/8/5615/2008/acp-8-5615-2008.html http://www.atmos-chem-phys.net/8/5615/2008/acp-8-5615-2008.pdf 5615 5626 2008-09-23 Measurements of UV irradiance within the area of one satellite pixel P. Weihs philipp.weihs@boku.ac.at M. Blumthaler H. E. Rieder A. Kreuter S. Simic W. Laube A. W. Schmalwieser J. E. Wagner A. Tanskanen Inst. for Meteorology, Department Water–Atmosphere–Environment, Univ. of Natural Resources and Applied Life Sciences (BOKU), Vienna, Austria Division for Biomedical Physics, Innsbruck Medical University, Innsbruck, Austria Inst. for Geography and Regional Research, Univ. of Vienna, Vienna, Austria Finnish Meteorological Inst., Helsinki, Finland Inst. of Medical Physics and Biostatistics, Univ. of Veterinary Medicine, Vienna, Austria now at: Inst. for Atmospheric and Climate Science, ETH Zurich, Zurich, Switzerland A measurement campaign was performed in the region of Vienna and its surroundings from May to July 2007. Within the scope of this campaign erythemal UV was measured at six ground stations within a radius of 30 km. First, the homogeneity of the UV levels within the area of one satellite pixel was studied. Second, the ground UV was compared to ground UV retrieved by the ozone monitoring instrument (OMI) onboard the NASA EOS Aura Spacecraft. During clear-sky conditions the mean bias between erythemal UV measured by the different stations was within the measurement uncertainty of ±5%. Short term fluctuations of UV between the stations were below 3% within a radius of 20 km. For partly cloudy conditions and overcast conditions the discrepancy of instantaneous values between the stations is up to 200% or even higher. If averages of the UV index over longer time periods are compared the difference between the stations decreases strongly. The agreement is better than 20% within a distance of 10 km between the stations for 3 h averages. The comparison with OMI UV showed for clear-sky conditions higher satellite retrieved UV values by, on the average, approximately 15%. The ratio of OMI to ground measured UV lies between 0.9 and 1.5. and strongly depends on the aerosol optical depth. For partly cloudy and overcast conditions the OMI derived surface UV estimates show larger deviation from the ground-based reference data, and even bigger systematic positive bias. Here the ratio OMI to ground data lies between 0.5 and 4.5. The average difference between OMI and ground measurements is +24 to +37% for partly cloudy conditions and more than +50% for overcast conditions. Arola, A., Kazadzis, S., Krotkov, N., Bais, A., Gröbner, J., and Herman, J. R.: Assessment of TOMS UV bias due to absorbing aerosols, J. Geophys. Res., 110(D23211), doi:10.1029/2005JD005913, 2005. Bhartia, P. K. and Wellemeyer, C.: TOMS version 8 Algorithm Theoretical Basis Document, http://toms.gsfc.nasa.gov, November 24, 2004. Cede, A., Luccini, E., Nuñez, L., Piacentini, R. D., Blumthaler, M., and Herman, J.: TOMS derived erythemal irradiance versus measurements at the stations of the Argentine UV Monitoring Network, J. Geophys. Res., 109(D08109), doi:10.1029/2004JD004519, 2004. Chubarova, N. E., Yurova, A. Y., Krotkov, N. A., and Herman, J. R.: Comparisons between ground measurements of broadband ultraviolet (300 to 380 nm) and total ozone mapping spectrometer ultraviolet estimates at Moscow from 1979 to 2000, Opt. Eng., 41(12), 2070–3081, 2002. Fioletov, V. E., Kerr, J. B., Wardle, D. I., Krotkov, N., and Herman, J. R.: Comparison of Brewer ultraviolet irradiance measurements with total ozone mapping spectrometer satellite retrievals, Opt. Eng., 41(12), 3051–3061, 2002. Herman, J. R., Krotkov, N. A., Celarier, E., Larko, D., and Labow, G.: Distribution of UV radiation at the Earth's surface from TOMS measured UV-backscattered radiances, J. Geophys. Res., 104, 12 059–12 076, doi:0.1029/1999JD900062, 1999. Huber M., Blumthaler, M., Schreder, J., Bais, A., and Topaloglou, C.: Effect of ambient temperature on Robertson-Berger type erythemal dosimeters, Appl. Optics, 41, 4273–4277, 2002. Kalliskota, S., Kaurola, J., Taalas, P., Herman, J. R., Celarier, E., and Krotkov, N.: Comparison of the daily UV doses estimated from Nimbus7/TOMS measurements and ground-based spectroradiometric data, J. Geophys. Res., 105, 5059–5067, doi:10.1029/1999JD900926, 2000. Kaurola, J., Taalas, P., Koskela, T., Borkowski, J., and Josefsson, W.: Long-term variations of UV-B doses at three stations in northern Europe, J. Geophys. Res., 105(D16), 20 813–20 820, doi:10.1029/2000JD900258, 2000. Kazantzidis, A., Bais, A. F., Gröber, J., Herman, J. R., Kazadzis, S., Krotkov, N., Kyrö, E., den Outer, P. N., Garane, K., Görts, P., Lakkala, K., Meleti, C., Slaper, H., Tax, R. B., Turunen, T., and Zerefos, C. S.: Comparison of satellite-derived UV irradiances with ground-based measurements at four European stations, J. Geophys. Res., 111, D13207, doi:10.1029/2005JD006672, 2006. Koepke, P., De Backer, H., Bais, A., Curylo, A., Eerme, K., Feister, U., Johnsen, B., Junk, J., Kazantzidis, A., Kryscin, J., Lindfors, A., Olseth, J. A., den Outer, P., Pribullova, A., Schmalwieser, A., Slaper, H., Staiger, H., Verdebout, J., Vuilleumier, L., and Weihs, P.: Modelling solar UV radiation in the past: algorithms and input data, Proc. SPIE, 6362, 1–11, 2006. Krotkov, N. A., Bhartia, P. K, Herman, J. R., Ahmad, Z., and Fioletov, V.: Satellite estimation of spectral surface UV irradiance 2: Effect of horizontally homogeneous clouds and snow, J. Geophys. Res., 106, 11 743–11 759, doi:10.1029/2000JD900721, 2001. Krotkov, N. A., Herman, J. R., Bhartia, P. K., Seftor, C., Arola, A., Kaurola, J., Kalliskota, S., Taalas, P., and Geogdzhaev, I. V.: Version 2 total ozone mapping spectrometer ultraviolet algorithm: problems and enhancements, Opt. Eng., 41(12), 3028–3039, 2002. Levelt, P. F., Hilsenrath, E., Leppelmeier, G. W., Van den Oord, G. H. J., Bhartia, P. K., Tamminen, J., De Haan, J. F., and Veefkind, J. P.: Scientific Objectives of the Ozone Monitoring Instrument, IEEE T. Geosci. Remote, 44(5), 1199–1208, 2006. Lindfors, A. and Vuilleumier, L.: Erythemal UV at Davos (Switzerland), 1926–2003, estimated using total ozone, sunshine duration, and snow depth, J. Geophys. Res., 110, D02104, doi:10.1029/2004JD005231, 2005. McKenzie, R. L., Seckmeyer, G., Bais, A. F., Kerr, J. B., and Madronich, S.: Satellite retrievals of erythemal UV dose compared with ground-based measurements at northern and southern midlatitudes, J. Geophys. Res., 106, 24 051–24 062, doi:10.1029/2001JD000545, 2001b. National Radiological Protection Board: Health effects from ultraviolet radiation: Report of an advisory group on non-ionising radiation, Doc. NRP, 13, 1, UK, 2002. Rieder, H. E., Holawe, F., Simic, S., Blumthaler, M., Krzysćin, J. W., Wagner, J., Schmalwieser, A., and Weihs, P.: Reconstruction of erythemal UV-levels for two stations in Austria: a comparison between alpine and urban regions, Atmos. Chem. Phys. Discuss., 8, 957–994, 2008. SCOPE: Effects of Increased Ultraviolet Radiation on Global Ecosystems, Scientific Committee on Problems of the Environment (SCOPE), 51 bd de Montmorency, 75016 Paris, France, 1993. SCOPE, Effects of Increased Ultraviolet Radiation on Biological Systems, Scientific Committee on Problems of the Environment (SCOPE), 51 bd de Montmorency, 75016 Paris, France, 1992. Stamnes, K., Tsay, S. C., Wiscombe, W., and Jayaweera, K.: Numerically stable algorithm for discrete-ordinate-method radiative transfer in multible scattering and emitting layered media, Appl. Optics, 27, 2502–2509, 1988. Tanskanen, A.: Lambertian Surface Albedo Climatology at 360 nm from TOMS Data Using Moving Time-Window Technique, Proc. XX Quadr. Oz. Symp., 1–8 June, Kos, Greece, 2004. Tanskanen, A., Krotkov, N. A., Herman, J. R., and Arola, A.: Surface Ultraviolet Irradiance from OMI, IEEE T. Geosci. Remote, 44, 1267–1271, 2006. Tanskanen, A., Lindfors, A., Määttä, A., Krotkov, N., Herman, J., Kaurola, J., Koskela, T., Lakkala, K., Fioletov, V., Bernhard, G., McKenzie, R., Kondo, Y., O'Neill, M., Slaper, H., DenOuter, P., Bais, A. F., and Tamminen, J.: Validation of daily erythemal doses from ozone Monitoring Instrument with ground-based UV measurement data, J. Geophys. Res., 112, D24S44, doi:10.1029/2007JD008830, 2008. United Nations Environment Program (UNEP): Environmental effects of ozone depletion: 1998 assessment, Nairobi, Kenya, 1998. Webb, A., Gröbner, J., and Blumthaler, M.: A Practical Guide to Operating Broadband Instruments Measuring Erythemally Weighted Irradiance, Office for Official Publications of the European Communities, Luxembourg, 21 pp., 2006, ISBN 92-898-0032-1, 2006. Wuttke, S., Verdebout, J., and Seckmeyer, G.: An improved algorithm for satellite-derived UV radiation, Photochem. Photobiol., 77(1), 52–57, 2003. World Meteorological Organization (WMO): Scientific Assessment of Ozone Depletion: 1994, Global Ozone Research and Monitoring Project, WMO Rep. N 37, Geneva, 1995.