ACPD Atmospheric Chemistry and Physics Discussions ACPD 1680-7375 Copernicus GmbH Göttingen, Germany 10.5194/acpd-7-17401-2007 Comparison of UV-RSS spectral measurements and TUV model runs for clear skies for the May 2003 ARM aerosol intensive observation period Michalsky J. J. 1 Kiedron P. W. 2 National Oceanic and Atmospheric Administration, Earth System Research Laboratory, 325 Broadway, Boulder, Colorado, 80305, USA Cooperative Institute for Research in Environmental Sciences, University of Colorado, 325 Broadway, Boulder, Colorado, 80305, USA 28 11 2007 7 6 17401 17427 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-discuss.net/7/17401/2007/acpd-7-17401-2007.html The full text article is available as a PDF file from http://www.atmos-chem-phys-discuss.net/7/17401/2007/acpd-7-17401-2007.pdf

The first successful deployment of the fully-operational ultraviolet rotating shadow-band spectroradiometer occurred during the May 2003 U.S. Department of Energy's Atmospheric Radiation Measurement program's Aerosol Intensive Observation Period. The aerosol properties in the visible range were characterized using redundant measurements with several instruments to determine the column aerosol optical depth, the single scattering albedo, and the asymmetry parameter needed as input for radiative transfer calculations of the downwelling direct normal and diffuse horizontal solar irradiance in clear-sky conditions. The Tropospheric Ultraviolet and Visible (TUV) radiative transfer model developed by Madronich and his colleagues at the U.S. National Center for Atmospheric Research was used for the calculations of the spectral irradiance between 300–360 nm. Since there are few ultraviolet measurements of aerosol properties, most of the input aerosol data for the radiative transfer model are based on the assumption that UV input parameters can be extrapolated from the visible portion of the spectrum. Disagreements between available extraterrestrial spectra, which are discussed briefly, suggested that instead of comparing irradiances that measured and modeled spectral transmittances between 300–360 nm should be compared for the seven cases studied. These cases included low to moderate aerosol loads and low to high solar-zenith angles. A procedure for retrieving single scattering albedo in the ultraviolet based on the comparisons of direct and diffuse transmittance is outlined.

 References Anderson, G. P., Berk, A., Acharya, P. K., Matthew, M. W., Bernstein, L. S., J. H.,, H. Dothe, Adler-Golden, S. M., Ratkowski, A. J., Felde, G. W., Gardner, J. A., Hoke, M. L., Richtsmeier, S. C., Pukall, B., Mello, J., and Jeong, L. S.: MODTRAN4: Radiative transfer modeling for remote sensing in algorithms for multispectral, hyperspectral, and ultraspectral imagery VI, edited by: Chen, S. and Descour, M. R., Proceedings of SPIE 4049-16, pp. 176–183, Orlando, Florida, April 24, 2000. Bernhard, G., Booth, C. R., and Ehramjian, J. C.: Version 2 data of the National Science Foundation's Ultraviolet Radiation Monitoring Network: South Pole, J. Geophys. Res.-Atmos., 109, D21207, doi:10.1029/2004JD004937, 2004. d'Almeida, G. A., Koepke, P., and Shettle, E. P.: Atmospheric Aerosols: Global Climatology and Radiative Characteristics. A. Deepak Publishing, Hampton, Virginia, USA, 1991. Clough, S. A., Iacono, M. J., and Moncet, J.-L.: Line-by-line calculation of atmospheric fluxes and cooling rates: Application to water vapor, J. Geophys. Res., 97, 15 761–15 785, 1992. Dubovik, O., Smirnov, A., Holben, B. N., King, M. D., Kaufman, Y. J., Eck, T. F., and Slutsker, I.: Accuracy assessments of aerosol optical properties retrieved from Aerosol Robotic Network (AERONET) Sun and sky radiance measurements, J. Geophys. Res.-Atmos., 105(D8), 9791–9806, 2000. Feister, U. and Grewe, R.: Spectral albedo measurements in the UV and visible region over different types of surfaces, Photochem. Photobiol., 62(4), 736–744, 1995. Gröbner, J. and Kerr, J. B.: Ground-based determination of the spectral ultraviolet extraterrestrial solar irradiance: Providing a link between space-based and ground-based solar UV measurements, J. Geophys. Res.-Atmos., 106(D7), 7211–7217, 2001. Gueymard, C. A.: The sun's total and spectral irradiance for solar energy applications and solar radiation models, Sol. Energy, 76, 423–453, 2004. Halthore, R. N. and Schwartz, S. E.: Comparison of model-estimated and measured diffuse downward irradiance at surface in cloud-free skies, J. Geophys. Res.-Atmos., 105, 20 165–20 177, 2000. Halthore, R. N., Miller, M. A., Ogren, J. A., Sheridan, P. J., Slater, D. W., and Stoffel, T.: Further developments in closure experiments for diffuse irradiance under cloud-free skies at a continental site, Geophys. Res. Lett., 31, L07111, doi:10.1029/2003GL019102, 2004. Harder, J., Lawrence, G., Fontenla, J., Rottman, G., and Woods, T.: The spectral irradiance monitor: Scientific requirements, instrument design, and operation modes, Sol. Phys., 203, 141–167, 2005a. Harder, J., Fontenla, J., Lawrence, G., Woods, T., and Rottman, G.: The spectral irradiance monitor: Measurement equations and calibration, Sol. Phys., 203, 169–203, 2005b. Harder, J., Fontenla, J., White, O., Rottman, G., and Woods, T.: Solar spectral irradiance variability comparisons of the SORCE SIM instruments with monitors of solar activity and spectral synthesis, Memorie della Societa Astronomica Italiena, 76, 735–742, 2005c. Kazantzidis, A., Balis, D. S., Bais, A. F., Kazadzis, S., Galani, E., and Kosmidis, E.: Comparison of Model Calculations with Spectral UV Measurements during the SUSPEN Campaign: The Effect of Aerosols, J. Atmos. Sci., 58, 1529–1539, 2001. Kassianov, E. I., Flynn, C. J., Ackerman, T. P., and Barnard, J. C.: Aerosol single-scattering albedo and asymmetry parameter from MFRSR observations during the ARM Aerosol IOP 2003, Atmos. Chem. Phys., 7, 3341–3351, 2007. Kiedron, P. W., Michalsky, J. J., Berndt, J. L., and Harrison, L. C.: Comparison of spectral irradiance standards used to calibrate shortwave radiometers and spectroradiometers, Appl. Optics, 38, 2432–2439, 1999. Kiedron, P. W., Harrison, L. H., Berndt, J. L., Michalsky, J. J., and Beaubien, A. F.: Specifications and performance of UV rotating shadowband spectroradiometer (UV-RSS), Proceedings of SPIE, vol. 4482, San Diego, California, 2001. Kiedron, P., Schlemmer, J., Slusser, J., and Disterhoft, P.: Validation of ozone and aerosol retrieval methods with UV Rotating Shadowband Spectroradiometer (RSS), Proceedings of SPIE, vol. 6362, Stockholm, Sweden, 2006. Kouremeti, N., Bais, A., Kazandzis, S., Blumthaler, M., and Schmitt, R.: A CCD spectrometer for direct solar irradiance and sky radiance measurements, in: Proceedings of the UV Conference "One Century of UV Radiation Research," edited by: Gröbner, J., 18–20 September 2007, Davos, Switzerland. Kurucz, R. L., Furenlid, I., Brault, J., and Testerman, L.: Solar flux atlas from 296 to 1300 nm, National Solar Observatory Atlas No. 1, Harvard Univ. Press, Cambridge, Mass., available at ftp://ftp.noao.edu/fts/fluxatl/, 1984. Kurucz, T. L.: Synthetic infrared spectra, Infrared Solar Physics, IAU Symp. 154, edited by: Rabin, D. M. and Jefferies, J. T., Kluwer, Acad., Norwell Massachusetts, 1992. Madronich, S.: The atmosphere and UV-B radiation at ground level. Environmental UV Photobiology, Plenum Press, 1–39, 1993. Mayer, B., Seckmeyer, G., and Kylling, A.: Systematic long-term comparison of spectral UV measurements and UVSPEC modeling results, J. Geophys. Res.-Atmos., 102(D7), 8755–8768, doi:10.1029/97JD00240, 1997. Mayer, B. and Kylling, A.: Technical note: The libRadtran software package for radiative transfer calculations – description and examples of use, Atmos. Chem. Phys., 5, 1855–1877, 2005. McKenzie, R. L., Kotkamp, M., and Ireland, W.: Upwelling UV spectral irradiances and surface albedo measurements at Lauder, New Zealand, Geophys. Res. Lett., 23, 14, 1761–1764, 1996. Michalsky, J. J., Anderson, G. P., Barnard, J., Delamere, J., Gueymard, C., Kato, S., Kiedron, P., McComiskey, A., and Ricchiazzi, P.: Shortwave radiative closure studies for clear skies during the Atmospheric Radiation Measurement 2003 Aerosol Intensive Observation Period, J. Geophys. Res.-Atmos., 111, D14S90, doi:10.1029/2005JD006341, 2006. 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.-Atmos., 108(D9), 4288, doi:10.1029/2002JD002360, 2003. Rottman, G., Harder, J., Fontenla, J., Woods, T., White, O., and Lawrence, G.: The Spectral Irradiance Monitor (SIM): Early Observations, Sol. Phys., 203, 205–224, 2005. Thuillier, G., Woods, T. N., Floyd, L., Hilsenrath, E., Cebula, R., Herse, M., and Labs, D.: Sun reference spectra from solar cycle 22 measurements, in: Solar Variability and its Effects on Climate, edited by: Pap, J. M., Fox, P., Frohlich, C., et al., Geophysical Monograph, 141, American Geophysical Union, 2004. vanHoosier, M. E.: Solar ultraviolet spectral irradiance data with increased wavelength and irradiance accuracy, in: Ultraviolet Atmospheric and Space Remote Sensing: Methods and Instrumentation, edited by: Huffman, R. E. and Stergis, C. G., Proc., SPIE Int. Soc. Opt. Eng., 2831, 57–64, 1996. Weihs, P. and Webb, A. R.: Accuracy of spectral UV model calculations 2. Comparison of UV calculations with measurements, J. Geophys. Res.-Atmos., 102(D1), 1551–1560, 1997. 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.-Atmos., 106(D15), 17 311–17 320, 2001.