ACP Atmospheric Chemistry and Physics ACP 1680-7324 Copernicus GmbH Göttingen, Germany 10.5194/acp-12-2297-2012 The influence of the spatial resolution of topographic input data on the accuracy of 3-D UV actinic flux and irradiance calculations Weihs P. 1 Wagner J. E. 1 Schreier S. F. 1 Rieder H. E. 2 3 Angelini F. 4 Blumthaler M. 5 Fitzka M. 1 Gobbi G. P. 4 Kift R. 6 Kreuter A. 5 Simic S. 1 Webb A. R. 6 Institute of Meteorology, University of Natural Resources and Life Sciences, Vienna, Austria Institute for Atmospheric and Climate Science, ETH Zurich, Zurich, Switzerland Department of Applied Physics and Applied Mathematics, Columbia University, New York, USA Institute of Atmospheric Sciences and Climate, ISAC-CNR, Rome, Italy Division for Biomedical Physics, Innsbruck Medical University, Innsbruck, Austria School of Earth, Atmospheric and Environmental Sciences, University of Manchester, Manchester, UK 01 03 2012 12 5 2297 2312 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/12/2297/2012/acp-12-2297-2012.html The full text article is available as a PDF file from http://www.atmos-chem-phys.net/12/2297/2012/acp-12-2297-2012.pdf

The aim of this study is to investigate the influence of the spatial resolution of a digital elevation map (DEM) on the three-dimensional (3-D) radiative transfer performance for both spectral ultraviolet (UV) irradiance and actinic flux at 305 nm. Model simulations were performed for clear sky conditions for three case studies: the first and second one using three sites in the Innsbruck area and the third one using three sites at the Sonnblick observatory and surrounding area. It was found that the DEM resolution may change the altitude at some locations by up to 500 m, resulting in changes in the sky obscured by the horizon of up to 15%. The geographical distribution of UV irradiance and actinic flux shows that with larger pixel size, uncertainties in UV irradiance and actinic flux determination of up to 100% are possible. These large changes in incident irradiance and actinic flux with changing pixel size are strongly connected to shading effects. The effect of the DEM pixel size on irradiance and actinic flux was studied at the six locations, and it was found that significant increases in irradiance and actinic flux with increasing DEM pixel size occurred at one valley location at high solar zenith angles in the Innsbruck area as well as for one steep valley location in the Sonnblick area. This increase in irradiance and actinic flux with increasing DEM resolution is most likely to be connected to shading effects affecting the reflections from the surroundings.

 References Anderson, G., Clough, S., Kneizys, F., Chetwynd, J., and Shettle, E.: AFGL Atmospheric Constituent Profiles (0–120 km), Tech. Rep. AFGL-TR-86-0110, AFGL (OPI), Hanscom AFB, MA 01736, USA, 1986. Arola, A., Lindfors, A., Natunen, A., and Lehtinen, K. E. J.: A case study on biomass burning aerosols: effects on aerosol optical properties and surface radiation levels, Atmos. Chem. Phys., 7, 4257–4266, http://dx.doi.org/10.5194/acp-7-4257-2007doi:10.5194/acp-7-4257-2007, 2007. Badosa, J., McKenzie, R. L., Kotkamp, M., Calbo, J., Gonzalez, J. A., Johnston, P. V., O'Neill, M., and Anderson, D. J.: Towards closure between measured and modelled UV under clear skies at four diverse sites, Atmos. Chem. Phys., 7, 2817–2837, http://dx.doi.org/10.5194/acp-7-2817-2007doi:10.5194/acp-7-2817-2007, 2007. Bais, A. F., Gardiner, B., Slaper, H., Blumthaler, M., Bernhard, G., McKenzie, R., Webb, A. R., Seckmeyer, G., Kjelstad, B., Koskela, T., Kirsch, P. J., Gröbner, J., Kerr, J. B., Kazadzis, S., Leszczynski, K., Wardle, D., Brogniez, C., Josefsson, W., Gillotay, D., Reinen, H., Weihs, P., Svenoe, T., Eriksen, P., Kuik, F. and Redondas, A.: The SUSPEN intercomparison of ultraviolet spectroradiometers, J. Geophys. Res., 106, 12 509–12 525, 2001. Bais, A. F., Madronich, S., Crawford., J., Hall, S. R., Mayer, B., Van Weele, M., Lenoble, J. Calvert,J. B., Cantrell, C. A., Shetter, R. E., Hofzumahaus, A., Koepke, P., Monks, P. S., Frost, G., McKenzie, R., Krotkov, N., Kylling, A., Swartz, W. H., Lloyd, S., Pfister, G., Martin, T. J., Roeth, E.-P., Griffioen, E., Ruggaber, A., Krol, M., Kraus, A., Edwards, G. D., Mueller, M., Lefer, B. L., Johnston, P., Schwander, H., Flittner, D., Gardiner, B. G., Barrick, J., and Schmitt, R.: International Photolysis Frequency Measurement and Model Intercomparison (IPMMI): Spectral actinic solar flux measurements and modeling, J. Geophys. Res., 108, 8543, http://dx.doi.org/10.1029/2002JD002891doi:10.1029/2002JD002891, 2003. Balis, D. S., Amiridis, V., Zerefos, C., Kazantzidis, A., Kazadzis, S., Bais, A. F., Meleti, C., Gerasopoulos, E., Papayannis, A., Matthias, V., Dier, H., and Andreae, M. O.: Study of the effect of different type of aerosols on UV-B radiation from measurements during EARLINET, Atmos. Chem. Phys., 4, 307–321, http://dx.doi.org/10.5194/acp-4-307-2004doi:10.5194/acp-4-307-2004, 2004. Blumthaler, M. and Amback, W.: Solar UVB-albedo of various surfaces, Photochem. Photobiol., 48, 85–88, 1988. Blumthaler, M., Ambach, W., Cede, A., and Staehelin, J.: Attenuation of erythemal effective irradiance by cloudiness at low and high altitude in the Alpine region, Photochem. Photobiol., 63, 193–196, 1996. Cahalan, R. F., Oreopoulos, L., Marshak, A., Evans, K. F., Davis, A., Pincus, R., Yetzer, K., Mayer, B.,Davies, R., Ackerman, T., Barker, H., Clothiaux, E., Ellingson, R., Garay, M., Kassianov, E., Kinne, S., Macke, A., Ohirok, W., Partain, P., Prigarin, S., Rublev, A., Stephens, G., Szczap, F., Takara, E., Varnai, T., Wen, G., and Zhuravleva, T.: The International Intercomparison of 3D Radiation Codes (I3RC): Bringing together the most advanced radiative transfer tools for cloudy atmospheres, B. Am. Meteor. Soc., 86, 1275–1293, 2005. Calbo, J., Pages, D., and Gonzalez, J.-A.: Empirical studies of cloud effects on UV radiation: a review, Rev. Geophys., 43, 155–183, 2005. Commission Internationale de l'Eclairage (CIE): 134/1, TC 6-26 Report: Standardization of the terms UV-A1, UV-A2 and UV-B, in Collection in Photobiology and Photochemistry, Comm. Int. de l'Eclairage, Vienna, Austria, 1999. Dahlback, A. and Stamnes, K.: A new spherical model for computing the radiation field available for photolysis and heating at twilight, Planetary and Space Science (ISSN 0032-0633), 39, 671–683, http://dx.doi.org/10.1016/0032-0633(91)90061-Edoi:10.1016/0032-0633(91)90061-E, 1991. Degünther, M., Meerkötter, R., Albold, A., and Seckmeyer, G.: Case study on the influence of inhomogeneous surface albedo on UV irradiance, Geophys. Res. Lett. 25, 3587–3590, 1998. Den Outer, P. N., Slaper, H., and Tax, R. B.: UV radiation in the Netherlands: Assessing long-term variability and trends in relation to ozone and clouds, J. Geophys. Res., 110, D02203, http://dx.doi.org/10.1029/2004JD004824doi:10.1029/2004JD004824, 2005. Den Outer, P. N., Slaper, H., Kaurola, J., Lindfors, A., Kazantzidis, A., Bais, A. F., Feister, U., Junk, J., Janouch, M., and Josefsson, W.: Reconstructing of erythemal ultraviolet radiation levels in Europe for the past 4 decades, J. Geophys. Res., 115, D10102, http://dx.doi.org/10.1029/2009JD012827doi:10.1029/2009JD012827, 2010. Feister, U. and Grewe, R.: Higher UV radiation inferred from low ozone levels at northern mid-latitudes in 1992 and 1993, Global Planet, Change, 11, 25–34, 1995. Gantner, L., Winkler, P., and Köhler, U.: A method to derive long-term time series and trends of UV-B radiation (1968–1997) from observations at Hohenpeissenberg (Bavaria), J. Geophys. Res., 105, 4879–4888, http://dx.doi.org/10.1029/1999JD900907doi:10.1029/1999JD900907, 2000. Gueymard, C.: Prediction and validation of cloudless shortwave solar spectra incident on horizontal, tilted, or tracking surfaces, Solar Energy, 82, 260–271, 2008. Hegglin, M. I. and Shepherd, T. G.: O<sub>3</sub>-N<sub>2</sub>O correlations from the Atmospheric Chemistry Experiment: Revisiting a diagnostic of transport and chemistry in the stratosphere, J. Geophys. Res., 112, D19301, http://dx.doi.org/10.1029/2006JD008281doi:10.1029/2006JD008281, 2007. 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, http://dx.doi.org/10.1029/1999JD900926doi: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, 20813–20820, http://dx.doi.org/10.1029/2000JD900258doi:10.1029/2000JD900258, 2000. Kazadzis, S., Bais, A. F., Balis, D., Zerefos, C. S., and Blumthaler, M.: Retrieval of down-welling UV actinic flux density spectra from spectral measurements of global and direct solar UV irradiance, J. Geophys. Res., 105, 4857–4864, 2000. Krotkov, N. A., Bhartia, P., Herman, J., Fioletov, V., and Kerr, J.: Satellite estimation of spectral surface UV irradiance in the presence of tropospheric aerosols 1. Cloud-free case, J. Geophys. Res., 103, 8779–8793, 1998. Krzyscin, J. W. and Puchalski, S.: Aerosol impact on the surface UV radiation from the ground-based measurements taken at Belsk, Poland, 1980–1996, J. Geophys. Res., 103, 16175–16181, http://dx.doi.org/10.1029/98JD00899doi:10.1029/98JD00899, 1998. Kylling, A., Albold, A., and Seckmeyer, G.: Transmittance of a cloud is wavelength-dependent in the UV-range: Physical interpretation, Geophys. Res. Lett., 24, 397–400, 1997. Kylling, A., Persen, T., Mayer, B. and Svenoe, T.: Determination of an Effective Spectral Albedo from ground based global and direct UV irradiance measurements, J. Geophys. Res., 105, 4949-4959, 2000. Kylling, A., Dahlback, A., and Mayer, B.: The effect of clouds and surface albedo on UV irradiances at a high latitude site, Geophys. Res. Lett., 27, 1411–1414, http://dx.doi.org/10.1029/1999GL011015doi:10.1029/1999GL011015, 2000. Kylling, A., Webb, A. R., Kift, R., Gobbi, G. P., Ammannato, L., Barnaba, F., Bais, A., Kazadzis, S., Wendisch, M., Jäkel, E., Schmidt, S., Kniffka, A., Thiel, S., Junkermann, W., Blumthaler, M., Silbernagl, R., Schallhart, B., Schmitt, R., Kjelstad, B., Thorseth, T. M., Scheirer, R., and Mayer, B.: Spectral actinic flux in the lower troposphere: measurement and 1-D simulations for cloudless, broken cloud and overcast situations, Atmos. Chem. Phys., 5, 1975–1997, http://dx.doi.org/10.5194/acp-5-1975-2005doi:10.5194/acp-5-1975-2005, 2005. 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, http://dx.doi.org/10.1029/2004JD005231doi:10.1029/2004JD005231, 2005. Longstreth, I., De Gruijl, F. R., Kripke, M. L., Abseck, S., Arnold, F., Slaper, H., Velders, G., Takizawa, Y. and Van der Leun, J. C.: Health risks, J. Photochem. Photobiol. B, 46, 20–33, 1998. Madronich, S.: Photodissociation in the Atmosphere: 1. Actinic Flux and the Effects of Ground Reflections and Clouds, J. Geophys. Res., 92, 9740–9752, 1987. 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. Mayer, B., Kylling, A., Madronich, S. and Seckmeyer, G.: Enhanced absorption of UV radiation due to multiple scattering in clouds: Experimental evidence and theoretical explanation, J. Geophys. Res. 103, 31 241–31 254, 1998. Mayer, B., Hoch, S. W., and Whiteman, C. D.: Validating the MYSTIC three-dimensional radiative transfer model with observations from the complex topography of Arizona's Meteor Crater, Atmos. Chem. Phys., 10, 8685–8696, http://dx.doi.org/10.5194/acp-10-8685-2010doi:10.5194/acp-10-8685-2010, 2010. McKenzie, R. L., Paulin, K. J. and Madronich, S.: Effects of snow cover on UV irradiance and surface albedo: A case study, J. Geophys. Res., 103, 785–792, 1998. McKenzie, R., Seckmeyer, G., Bais, A., Kerr, J., and Madronich, S.: Satellite retrievals of erythemal UV dose compared with groundbased measurements at northern and southern midlatitudes, J. Geophys. Res., 106, 24051–24062, 2001. Nader, J. S. and White, N.: Volumetric measurement of ultraviolet energy in an urban atmosphere, Environ. Sci. Technol., 3, 848–854, 1969. National Radiological Protection Board: Health effects from ultraviolet radiation, Report of an advisory group on non-ionising radiation, Doc. NRP, 13, p 1, UK, 2002. Pachard, E., Lenoble, J., Brogniez, C., Masserot, D., and Bocquet, J. L.: Ultraviolet spectral irradiance in the French Alps: Results of two campaigns, J. Geoph. Res., 104, 16777–16784, 1999. Reuder, J. and Schwander, H.: Aerosol effects on UV radiation in nonurban regions, J. Geophys. Res., 104, 4065–4077, 1999. Ricchiazzi, P. and Gautier, C.: Investigation of the effect of surface heterogeneity and topography on the radiation environment of Palmer Station, Antarctica, with a hybrid 3-D radiative transfer model, J. Geoph. Res., 103, 6161–6176, 1998. Rieder, H. E., Holawe, F., Simic, S., Blumthaler, M., Krzyscin, J. W., Wagner, J. E., Schmalwieser, A. W., and Weihs, P.: Reconstruction of erythemal UV-doses for two stations in Austria: a comparison between alpine and urban regions, Atmos. Chem. Phys., 8, 6309–6323, http://dx.doi.org/10.5194/acp-8-6309-2008doi:10.5194/acp-8-6309-2008, 2008. Rieder, H. E., Staehelin, J., Weihs, P., Vuilleumier, L., Maeder, J. A., Holawe, F., Blumthaler, M., Lindfors, A., Peter, T., Simic, S., Spichtinger, P., Wagner, J. E., Walker, D., and Ribatet, M.: Relationship between high UV-doses, total ozone, surface albedo and cloudiness: An analysis of 30 years of data from Switzerland and Austria, Atmos. Res., 98, 9–20, 2010. Sabburg, J. M., Parisi, A. V., and Kimlin, M. G.: Enhanced spectral UV irradiance: a 1 year preliminary study, Atmos. Res., 66, 261–272, 2003. Schafer, J. S., Saxena, V. K., Wenny, B. N., Barnard, W., and De Luisi, J. J.: Observed influence of clouds on ultraviolet-B radiation, Geophys. Res. Lett., 23, 2625–2628, 1996. Scheirer, R. and Macke, A.: On the accuracy of the independent column approximation in calculating the downward fluxes in the UVA, UVB, and PAR spectral ranges. J. Geophys. Res., 106, 14301–14312, 2001. Scheirer, R. and Macke, A.: Cloud inhomogeneity and broadband solar fluxes. J. Geophys. Res., 108, 4599, http://dx.doi.org/10.1029/2002JD003321doi:10.1029/2002JD003321, 2003. Schmalwieser, A. W., Schauberger, G., Weihs, P., Simic, S., Stubi, R., Janouch, M., and Coetzee, G. J. R.: Preprocessing of total ozone content as an input parameter to UV index forecast calculations, J. Geophys. Res. 108, 4176–4189, 2003. Schmucki, D. A. and Philipona, R.: Ultraviolet radiation in the alps: The altitude effect, Opt. Eng., 41, 3090–3095, 2002. Schwander, H., Koepke, P., and Ruggaber, A.: Uncertainties in modeled UV irradiances due to limited accurancy and availability of input data, J. Geophys. Res., 102, 9419–9430, http://dx.doi.org/10.1029/97JD00244doi:10.1029/97JD00244, 1997. Seckmeyer, G., Erb, R., and Albold, A.: Transmittance of a cloud is wavelength-dependent in the UV-range, Geophys. Res. Lett., 23, 2753–2755, 1996. Simic, S., Weihs, P., Vacek, A., Kromp-kolb, H., and Fitzka, M.,: Spectral UV measurements in Austria from 1994 to 2006: Investigations of short- and long-term changes, Atmos. Chem. Phys., 8, 7033–7043, http://dx.doi.org/10.5194/acp-8-7033-2008doi:10.5194/acp-8-7033-2008, 2008. Simic, S., Fitzka, M., Schmalwieser, A., Weihs, P., and Hadzimustafic, J.: Factors affecting UV irradiance at selected wavelengths at Hoher Sonnblick, Atmos. Res., 101, 869–878, http://dx.doi.org/10.1016/j.atmosres.2011.05.022doi:10.1016/j.atmosres.2011.05.022, 2011. Slaper, H., Velders, G. J. M., Daniel, J. S., De Gruijl, F. R., and Van der Leun, J. C.: Estimates of ozone depletion and skin cancer incidence to examine the Vienna Convention achievements, Nature, 384, 256–258, 1996. Smith, R.C., Wan, Z., and Baker, K. S.: Ozone depletion in Antarctica: modeling its effect on solar UV irradiance under clear-sky conditions, J. Geophys. Res. 97, Issue C5, 7383–7397, 1992. Smolskaia, I., Nunez, M., and Kelvin, M.: Measurements of Erythemal Irradiance near Davis Station, Antarctica: Effect of Inhomegeneous Surface Albedo, Geoph. Res. Lett., 26, 1381–1384, 1999. Smolskaia, I., Masserot, D., Lenoble, J., Brogniez, C., and De La Casiniere, A.: Retrieval of the ultraviolet effective snow albedo during 1998 winter campaign in the French Alps, Appl. Opt., 42, 1583–1587, 2003. Staiger, H., Den Outer, P. N., Bais, A. F., and Vuilleumier, L.: Hourly resolved cloud modification factors in the ultraviolet, Atmos. Chem. Phys., 8, 2493–2508, http://dx.doi.org/10.5194/acp-8-2493-2008doi:10.5194/acp-8-2493-2008, 2008. Thiel, S., Steiner, K., and Seidlitz, H. K.: Modification of global erythemally effective irradiance by clouds, Photchem. Photobiol., 65, 969–973, 1997. Thiel, S., Ammannato, L., Bais, A., Bandy, B., Blumthaler, M., Bohn, B., Engelson, E., Gobbi, G. B., Gröbner, J., Jäkel, E., Junkermann, W., Kazadzis, S., Kift, R., Kjelstad, B., Kouremeti, N., Kylling, A., Mayer, B., Monks, P. S., Reeves, C. E., Schallhart, B., Scheirer, R., Schmidt, S., Schmitt, R., Schreder, J., Silbernagl, R., Topaloglou, C., Thorseth, T. M., Webb, A. R., Wendisch, M., and Werle, P.: Influence of clouds on the spectral actinic flux density in the lower troposphere (INSPECTRO): overview of the field campaigns, Atmos. Chem. Phys., 8, 1789–1812, http://dx.doi.org/10.5194/acp-8-1789-2008doi:10.5194/acp-8-1789-2008, 2008. United Nations Environment Program (UNEP): Environmental effects of ozone depletion: 1998 assessment, Nairobi, Kenya, 1998. Vanicek, K., Frei, T., Litynska, Z., and Schmalwieser, A.: UV-index for the public: A guide for publication and interpretation of solar UV index forecasts for the public prepared by theWorking Group 4 of the COST-713 action "UVB forecasting", Eur. Coop. Field Sci. Tech. Res., Brussels, 2000. Van Weele, M., De Arellano, J. V.-G., and Kuik, F.: Combined measurements of UV-A actinic flux, UV-A irradiance and global radiation in relation to photodissociation rates, Tellus, 47B, 353–364, 1995. Wagner, J. E, Angelini, F., Arola, A., Blumthaler, M., Fitzka, M., Gobbi, G. P., Kift, R., Kreuter, A., Rieder, H. E., Simic, S., Webb, A., and Weihs, P.: Comparison of surface UV irradiance in mountainous regions derived from satellite observations and model calculations with ground based measurements. Met. Zeitschr., 19, 481–490, 2010. Wagner, J. E, Angelini, F., Blumthaler, M., Fitzka, M., Gobbi, G. P., Kift, R., Kreuter, A., Rieder, H. E., Simic, S., Webb, A., and Weihs, P.: Investigation of the 3-D actinic flux field in mountainous terrain. Atmos. Res., 102, 300–310, 2011. Webb, A. B., Bais, A. F., Blumthaler, M., Gobbi, G. P., Kylling, A., Schmitt, R., Thiel, S., Barnaba, F., Danielsen, T., Junkermann, W., Kazantzadis, A., Kelly, P., Kift, R., Liberti, G. L., Misslbeck, M., Schallhart, B., Schreder, J., and Topaloglou, C.: Measuring spectral actinic flux and irradiance: Experimental results from the Actinic Flux Determination from Measurements of Irradiance (ADMIRA) project, J. Atmos. Ocean Technol., 19, 1049–1062, 2002. Weihs, P. and Webb, A.: Accuracy of spectral UV model calculations: 2 – Comparison of UV calculations with measurements, J. Geophys. Res., 102, 1551–1560, http://dx.doi.org/10.1029/96JD02621doi:10.1029/96JD02621, 1997. Weihs, P., Simic, S., Laube, W., Mikielewicz, W., Rengarajan, G., and Mandl, M.: Albedo influences on surface UV irradiance at the Sonnblick High Mountain Observatory (3106 m altitude), J. Appl. Met., 38, 1599–1610, 1999. Weihs, P., Lenoble, J., Blumthaler, M., Martin, T., Seckmeyer, G., Philipona, R., De La Casiniere, A., Sergent, C., Gröbner, J., Cabot, T., Masserot, D., Pichler, T., Pougatch, E., Rengarajan, G., Schmucki, D., and Simic, S.: Modelling the effect of an inhomogeneous surface albedo on incident UV radiation in mountainous terrain: Determination of an effective surface albedo, Geophys. Res. Lett., 28, 3111–3114, http://dx.doi.org/10.1029/2001GL012986doi:10.1029/2001GL012986, 2001. Wenny, B. N., Schafer, J. S., De Luisi, J. J., Saxena, V. K., Barnard, W. F., Petropavlovskikh, I. V., and Vergamini, A. J.: A study of regional aerosol radiative properties and effects on ultraviolet-B radiation, J. Geophys. Res., 103, 17083–17097, 1998. World Health Organization (WHO): Global Solar UV Index – A practical guide, 2002. World Health Organization (WHO): Environmental Burden of Disease Series No. 13 – Solar Ultraviolet radiation, 2006.