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Estimation of pedestrian level UV exposure under treesAuthor(s): Richard H. Grant; Gordon M. Heisler; Wei Gao
Source: Photochemistry and Photobiology. 75(4): 369-376.
Publication Series: Scientific Journal (JRNL)
Station: Northern Research Station
PDF: View PDF (870.91 KB)
DescriptionTrees influence the amount of solar UV radiation that reaches pedestrians. A three-dimensional model was developed to predict the ultraviolet-B (UV-B) irradiance fields in open-tree canopies where the spacing between trees is equal to or greater than the width of individual tree crowns. The model predicted the relative irradiance (fraction of above-canopy irradiance) under both sunlit and shaded conditions under clear skies with a mean bias error of less than 0.01 and a root mean square error of 0.07. Both model and measurements showed that the locations people typically perceive as shady, low-irradiance locations in the environment can actually have significant UV-B exposure (40-60% of that under direct sunlight). The relationship of tree cover in residential neighborhoods to erythema1 UV-B exposure for children and adults was modeled for the 4 h around noon in June and July. Results showed that human exposures (on the horizontal) in cities located at 15 and 30? latitudes are nearly identical. For latitudes between 15 and 60?, ultraviolet protection factors (UPF) were less than 2 for less than 50% tree cover. A UPF of 10 was possible at all latitudes for tree cover of 90%.
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CitationGrant, Richard H.; Heisler, Gordon M.; Gao, Wei. 2002. Estimation of pedestrian level UV exposure under trees. Photochemistry and Photobiology. 75(4): 369-376.
- Ultraviolet radiation, human health, and the urban forest
- Individual- and scattered-tree influences on ultraviolet irradiance
- Urban forest influences on exposure to UV radiation and potential consequences for human health
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