Horizontal and sun-normal spectral biologically effective ultraviolet irradiances

A. V. Parisi*, M. G. Kimlin

*Corresponding author for this work

Research output: Contribution to journalArticleResearchpeer-review

51 Citations (Scopus)


The dependence of the spectral biologically effective solar UV irradiance on the orientation of the receiver with respect to the sun has been determined for relatively cloud-free days at a sub-tropical Southern Hemisphere latitude for the solar zenith angle range 35-64°. For the UV and biologically effective irradiances, the sun-normal to horizontal ratio for the total UV ranges from 1.18 ± 0.05 to 1.27 ± 0.06. The sun-normal to horizontal ratio for biologically effective irradiance is dependent on the relative effectiveness of the relevant action spectrum in the UV-A waveband. In contrast to the total UV, the diffuse UV and diffuse biologically effective irradiances are reduced in a sun-normal compared with a horizontal orientation by a factor ranging from 0.70 ± 0.05 to 0.76 ± 0.03.

Original languageEnglish
Pages (from-to)70-74
Number of pages5
JournalJournal of Photochemistry and Photobiology B: Biology
Issue number1-3
Publication statusPublished - 1 Nov 1999
Externally publishedYes


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