Journal cover Journal topic
Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
Atmos. Chem. Phys., 4, 2543-2552, 2004
© Author(s) 2004. This work is licensed under
the Creative Commons Attribution-NonCommercial-ShareAlike 2.5 License.
14 Dec 2004
Improved sky imaging for studies of enhanced UV irradiance
J. M. Sabburg1 and C. N. Long2 1Centre for Astronomy, Solar Radiation and Climate, Faculty of Sciences, Univ. Southern Queensland, Toowoomba, Australia
2Pacific Northwest National Laboratory, Richland, WA, USA
Abstract. A recent World Meteorological Organisation report discussed the importance of continued study of the effect of clouds on the solar UV radiation reaching the earth's surface. The report mentions that the use of all-sky imagery offers the potential to understand and quantify cloud effects more accurately. There are an increasing number of studies investigating the enhancement of surface solar, UV irradiance, and UV actinic flux, using automated CCD and sky imagers. This paper describes new algorithms applicable to a commercially available all-sky imager (TSI-440), for research investigating cloud enhanced spectral UV irradiance. Specifically, these include three new algorithms relating to cloud amount at different spatial positions from 1) zenith and 2) from the solar position and 3) the visible brightness of clouds surrounding the sun. A possible relationship between UV enhancement and the occurrence of near-sun cloud brightness is reported based on this preliminary data. It is found that a range of wavelength dependent intensities, from 306 to 400 nm, can occur in one day for UV enhancements. Evidence for a possible decreasing variation of intensity with longer wavelengths is also presented.

Citation: Sabburg, J. M. and Long, C. N.: Improved sky imaging for studies of enhanced UV irradiance, Atmos. Chem. Phys., 4, 2543-2552,, 2004.
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