ACP Atmospheric Chemistry and Physics ACP 1680-7324 Copernicus GmbH Göttingen, Germany 10.5194/acp-8-3583-2008 Modelling UV irradiances on arbitrarily oriented surfaces: effects of sky obstructions Hess M. 1 Koepke P. 1 Meteorological Institute of the L.-M. University, Munich, Germany 07 07 2008 8 13 3583 3591 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/8/3583/2008/acp-8-3583-2008.html The full text article is available as a PDF file from http://www.atmos-chem-phys.net/8/3583/2008/acp-8-3583-2008.pdf

A method is presented to calculate UV irradiances on inclined surfaces that additionally takes into account the influence of sky obstructions caused by obstacles such as mountains, houses, trees, or umbrellas. With this method it is thus possible to calculate the impact of UV radiation on biological systems, such as, for instance, the human skin or eye, in any natural or artificial environment. The method, which consists of a combination of radiation models, is explained here and the accuracy of its results is demonstrated. The effect of a natural skyline is shown for an Alpine ski area, where the UV irradiance even on a horizontal surface may increase due to reflection from snow by more than 10 percent. In contrast, in a street canyon the irradiance on a horizontal surface is reduced to 30% in shadow and to about 75% for a position in the sun.

 References Arola, A., Kalliskota, S., den Outer, P.N., Edvardsen, K., Hansen, G., Koskela, T., martin, T.J., Matthijsen, J., Meerkötter, R., Peeters, P., Seckmeyer, G., Simon, P., Slaper, H., Taalas, P., and Verdebout, J.: Four UV mapping procedures using satellite data and their validation against ground-based UV measurements, K. Geophys. Res., 107, ACL11, 1–11, 2002. Bais, A., Lubin, D., Arola, A., Bernhard, G., Blumthaler, M., Chubarova, N., Erlick, C., Gies, H. P., Krotkov, N., Lantz, K., Mayer, B., McKenzie, R.L., Piacentini, R. D., Seckmeyer, G., Slusser, J. R., and Zerefos, C. S.: Surface ultraviolet radiation: Past, present, and future, Chapter 7 in: Scientific Assesment of Ozone Deplition: 2006. Global ozone and Monotoring Project. Report No. 50, World Meteorological organization, Geneva, 7.1–7.53, 2007. Blumthaler, M. and Ambach, W.: Solar UVB albedo of various surfaces, Photochem. Photobiol, 48(1), 85–88, 1988 Bucars, N.: Regionale und lokale Albedo im UV-Spektralbereich, Diploma-thesis, Meteorolog. Inst. Univ. Munich, 46 p., 2006. CIE: A reference action spectrum for ultraviolet induced erythemal in human skin, CIE research note, CIE Journal 6, 17–22, 1987. DeBacker, H., Koepke, P., Bais, A., de Cabo, X., Frei, T., Gillotay, D., haite, C., Heikkilä, A., Kaqzantzidis, A., Koskela, T., Kyrö, E., Lapeta, b., Lorente, J., Masson, K., Mayer, B., Plets, H., Redondas, A., Renaud, A., Schauberger, G., Schmalwieser, G., Schwander, H., Vanicek, K.: Comparison of measured and modeled UV indices for the assessment of health risks, Meteorol. Appl., 8, 267–277, 2001. Gao, W., Grant, R. H., Heisler, G. M., Slusser, J. R.: A Geometric Ultraviolet-B Radiation Transfer Model Applied to Vegetation Canopies, Agron. J., 94, 475–482, 2002. Grenfell, T. C. and Warren, S. G.: Reflection of solar radiation by the Antarctic snow surface at ultraviolet, visible, and near-infrared wavelengths, J. Geophys. Res., 99(D6), 18 669–18 684, 1994. Grifoni, D., Carreras, G., Sabatini, F., and Zipoli, G.: UV hazard on a summertime day under Mediterranean conditions and protective role of a beach umbrella, Int. J. Biometeorolog., 50 (2), 75–82, 2005. Hess, M., Koepke, P., and Schult, I.: Optical properties of aerosols and clouds: the software package OPAC, Bull. Am. Met. Soc., 79, 831–844, 1998. Kimlin, M. G. and Parisi, A. V.: Comparison of the spectral biologically effective solar ultraviolet in adjacent tree shade and sun, Phys. Med. Biol., 44, 2071–2080, 1999. Knuschke, P., Unverricht, I., Ott, G., and Janssen, M.: Personenbezogene Messung der UV-Exposition von Arbeitnehmern im Freien, Abschlussbericht zum Projekt F1777 im Auftrag der Bundesanstalt für Arbeitsschutz und Arbeitsmedizin, 2007. Koepke, P., Bais, A., Balis, D., Buchwitz, M., Backer, H.D., Cabo, X.D., Eckert, P., Erikson, P., Gillotay, D., Heikkilä, A., Koskela, T., Lapeta, B., Litynska, Z., Lorente, J., Mayer, B., Renaud, A., Ruggaber, A., Schauberger, G., Seckmeyer, G., Seifert, P., Schmalwieser, A., Schwander, H., Vanicek, K., and Weber, M.: Comparison of models used for UV Index calculations, Photochem. Photobiol., 67(6), 657–662, 1998. Koepke, P. and Mech, M.: UV irradiance on arbitrarily oriented surfaces: variation with atmospheric and ground properties, Theor. Appl. Climatol., 81, 25–32, 2005. Koepke, P., Anwender, D., Mech, M., Oppenrieder, A., Reuder, J., Ruggaber, A., Schreier, M., Schwander, H., and Schween, J.: Actual state of the UV radiation transfer model package STAR, in Fischer and Sohn (Eds.) IRS2004: Current Problems in Atmospheric Radiation, A. Deepak Publ., Hampton, USA, 71–74, 2006. Mc Kenzie, R. L., Paulin, K. J., and Kotkamp, M.: Erythemal UV Irradiances at Lauder, New Zealand: Relationship between horizontal and normal incidence, Photochem. Photobiol., 66(5) 683–689, 1997. Mech, M. and Koepke, P.: Model for UV irradiance on arbitrarily oriented surfaces, Theor. Appl. Climatol., 77, 151–158, 2004. Parisi, A. V. and Kimlin, M. G., Horizontal and sun-normal spectral biologically effective ultraviolet irradiances. J Photochem. Photobiol. B: Biol, 53, 70–74, 1999. Philipona R., Schilling A., and Schmucki D.: Albedo enhanced maximum UV irradiance measured on surfaces orientated normal to the Sun. Photochem. Photobiol. 73(4), 366–375, 2001 Ruggaber, A., Dlugi, R., and Nakajima, T.: Modelling radiation quantities and photolysis frequencies in the troposphere, J. Atmos. Chem., 18, 171–210, 1994. Schween, J. and Koepke, P.: Modelling the UV-exposure within a plant stand during a vegetation period, Meteor. Z., 14(2), 129–135, 2005. Seckmeyer, G., Pisulla, D., Glandorf, M., HENRIQUES; D., Johnsen, B., Webb, A., Siani, A:M. Bais, A., Kjeldstad, B., Brogniez, C., Lenoble, J., Gardiner, B., Kirsch, P., Koskela, T., Kaurola, J., Uhlmann, B., Slaper, H., den Outer, P., Janouch, M., Werle, P., Gröbner, J., Mayer, B., de la Casiniere, A., Simic, S., and Carvalho, F.: Variability of UV irradiance in Europe, Photochem. Photobiol., 83, 1–8, 2007. Staiger, H. and Koepke, P.: UV index forecasting on a global scale, Meteorolog. Zeitschrift, 14(2) 259–270, 2005. Turnbull, D. and Parisi, A. V.: Spectral UV in public shade settings, J. Photochem. Photbiol.: B Biol., 69, 13–19, 2003. Verdebout, J.: A European satellite-derived UV climatology available for impact studies, Radiat. Prot. Dosim, 111(4), 407–411, 2004. Webb, A. R, Weihs, P., and Blumthaler, M.: Spectral UV irradiance on vertical surfaces: a case study. Photochem Photobiol, 69(4), 464–470, 1999. WMO: Report of the WMO meeting of experts on UVB measurements, data quality and standardization of UV indices. Report 95, World Meteorological Organization, Geneva, Switzerland. Les Diablerets, 1994. WMO: Report of the WMO-WHO meeting of experts on standardization of UV indices and their dissemination to the public. Report 127, World Meteorological Organization, Geneva, Switzerland. Les Diablerets, 1997.