Atmospheric Chemistry and Physics www.atmos-chem-phys.net 1680-7316 1680-7324 8 12 2008 10.5194/acp-8-3247-2008 http://www.atmos-chem-phys.net/8/3247/2008/ http://www.atmos-chem-phys.net/8/3247/2008/acp-8-3247-2008.html http://www.atmos-chem-phys.net/8/3247/2008/acp-8-3247-2008.pdf 3247 3253 2008-06-27 Study of suitability of AvaSpec array spectrometer for solar UV field measurements I. Ansko K. Eerme kalju@aai.ee S. Lätt M. Noorma U. Veismann Tartu Observatory, 61602, Tõravere, Estonia Tartu University, Ülikooli 18, 50090, Tartu, Estonia A system to record the ultraviolet (UV) spectra of atmospheric global irradiance with the miniature fiber optic spectrometer AvaSpec-256 was developed for continuous computer-aided spectrometry at Tartu Observatory in 2005. As a result, the database of spectra recorded with 15-min-interval round 24 h over 300–400 nm, has been developed. The quantities retrieved from the spectra have been compared with those measured by the Scintec erythemal UV-SET sensor and the Kipp & Zonen narrowband 306 nm sensor. Almost clear and overcast days were selected for comparison. Reliable results on the spectral distribution of the UV global irradiance as well as the integrated daily spectral doses could be obtained at least during the bright half-year. The results were compared with the calculations performed by means of the LibRadtran package. The biases in irradiance were significant at SZA above 70–75&deg;. At dominating larger SZA the recorded values need sophisticated corrections and remain less reliable. At lower latitudes than that of the study site (58.3&deg;), the reliability of the spectrometer is expected to increase due to a smaller contribution of data measured at large SZA. <br></br> The variations of the ratio of UV-A/UV-B irradiance, retrieved from the spectra, were investigated. Also the covariation of the narrowband 306 nm irradiance and the irradiance integrated over the whole UV-B range was studied. The biases between the UV-A/UV-B irradiances calculated by means of the LibRadtran package and measured with the AvaSpec were small at SZA below 70&deg;. At larger SZA the values of the ratio as well as the biases increased, significantly depending on total ozone. Basics of Spectral Measurements: JETI Technische Instrumente GMBH, Jena, 47 pp., 2003. Berwick, M. and Kesler, D.: Ultraviolet Radiation Exposure, Vitamin D and Cancer, Photochem. Photobiol., 81, 1261–1266, 2005. Brown, S. W., Johnson, B. C., Freinholz, M. E., Yarbrough, M. A., Flora, S. J., Lykke, K. R., and Clark, D. K.: Stray-light correction algorithm for spectrographs, Metrologia, 40, 581-584, 2003. Brönnimann, S., Eugster, W., and Wanner, H.: Photo-oxidant chemistry in the polluted boundary layer under changing UV-B radiation, Atmos. Environ., 35, 3789–3797, 2001. Eerme, K., Veismann, U., and Lätt, S.: Proxy-based reconstruction of erythemal UV doses over Estonia for 1955–2004, Ann. Geophys., 24, 1767–1782, 2006. Edwards, G. D. and Monks, P. S.: Performance of a single-monochromator diode array spectrometer for the determination of actinic flux and atmospheric photolysis frequencies, J. Geophys. Res., 108, 8546, doi:10.1029/2002JD002844, 2003. Grant, W. B., Garland, C. F., and Holick, M. F.: Comparisons of estimated Economic Burdens due to Insufficient Solar Ultraviolet Irradiance and Vitamin D and Excess Solar UV Irradiance for the United States, Photochem. Photobiol., 81, 1276–1286, 2005. Gröbner, J., Blumthaler, M., Kazadzis, S., Bais, A., Webb, A., Schreder, J., Seckmeyer, G., and Rembges, D.: Quality assurance of spectral solar UV measurements: results from 25 UV monitoring sites in Europe, 2002 to 2004, Metrologia, 43, S66–S71, 2006. Gröbner, J., Rembges, D., and Bais, A.: Quality assurance of reference standards from nine European solar-ultraviolet monitoring laboratories, Appl. Optics, 41, 4278–4282, 2002. http://www.muk.uni-hannover.de/~seckmeyer/EDUCE/database.html: A short and Friendly Guide (S&FG) to the preparation of spectral irradiance data in Flextor format in readiness for submission to the European UV Database. JETI Technische Instrumente GmbH: Basics of Spectral Measurement, 53 pp., http://www.jeti.com/down/basics/basics.pdf ,last access: 25 July 2008, Jena May 2005. Kostkowski, H. J.: Reliable Spectroradiometry., 1 ed. Spectroradiometry Consulting, La Plata, MD, 609 pp., 1997. Kutser, T., Veismann, U., Reinart, A., Erm, A., Herlevi, A., and Kallio, K.: Results of Light Absorption/Attenuation Measurements in Finnish and Estonian lakes in Summer 1997, Proc. Estonian Acad. Sci. Biol. Ecol., 48, 46–62, 1999. Lehmann, B.: The Vitamin D<sub>3</sub> Pathway in Human Skin and its Role for Regulation of Biological Processes, Photochem. Photobiol., 81, 1246–1251, 2005. Mayer, B. and Kylling, A.: Technical note: The LibRadtran software package for radiative transfer calculations – description and examples of use, Atmos. Chem. Phys. Discuss., 5, 1319–1381, 2005. Neale, P. J., Helbing, E. W., and Day, T. A.: Symposium-in-Print: UV Effects in Aquatic and Terrestrial Environments Introduction, Photochem. Photobiol., 83, 775–776, 2007. Oliver, H. and Moseley, H.: The use of diode array spectrometers for dosimetry and phototherapy, Phys. Med. Biol., 47, 4411–4421, 2002. Seckmeyer, G., Bais, A., Bernhard, G., Blumthaler, M., Booth, C. R., Disterhoft, P., Eriksen, P., McKenzie, R. L., Miyauchi, M., and Roy, C.: Instruments to Measure Solar Ultraviolet Irradiance. Part 1: Spectral Instruments, in: Global Atmospheric Watch, Report No. 125, 30 pp., World Meteorological Organization, Geneva, Switzerland, 2001. Sullivan, J. H., Gitz III, D. C., Liu-Gitz, L., Xu, C., Gao, W., and Slusser, J.: Coupling Short-Term Changes in Ambient UV-B levels with Induction of UV-Screening Compounds, Photochem. Photobiol., 83, 863–870, 2007. WMO (World Meteorological Organization): Scientific Assessment of Ozone Depletion: 2006. Global Ozone Research and Monitoring Project – Report No. 50, 572 pp., Geneva Switzerland, 2007. Ylianttila, L., Visuri, R., Huurto, L., and Jokela, K.: Evaluation of a Single-monochromator Diode Array Spectroradiometer for Sunbed UV-radiation Measurements, Photochem. Photobiol., 81, 333–341, 2005. Zong, Y., Brown, S. W., Johnson, B. C., Lykke, K. R., and Ohno, Y.: Simple spectral stray light correction method for array spectroradiometers, Appl. Optics, 45, 1111–1119, 2006.