photobiologyWavebands (version 0.4.1)

UVI: Calculate UVI from spectral irradiance

Description

UVI (UV Index) is a unitless quantity based on erythema BSWF, that gives an easy to interpret UV measure, mainly meant for informing general public about sunburn risk.

Usage

UVI(spct, std = "NOAA")

Arguments

spct

a source.spct object

std

"WWO" (250 nm to 400 nm), "NOAA" (286.5 nm to 400 nm)

Value

a numeric value for the unitless UVI (This is a value on a continuous scale, rather than the discrete scale normally used.)

Details

Two different definitions of UV Index are implemented in this package. Setting std="NOAA" follows the definition in Kiedron et al. (2007) but using CIE98 as SWF. NOAA definition discards wavelengths shorter than 286.5 nm as when calculated based on spectral data from Brewer instruments. "WMO" uses the internationally accepted lower limit at 250 nm (see WHO, 2002). "NOAA" is the default as this is safer with noisy data for solar radiation measured at ground level, and in this case the value of UVI should be correct, and almost identical except for errors caused by noise at shorter wavelengths. However, when calculating UVI from radiation spectra from UV lamps, "WMO" should be used, as most UV lamps do emit some radiation between 250 nm and 286.5 nm.

References

WHO (2002) Global Solar UV Index: A Practical Guide. ISBN 92 4 159007 6, WHO, Geneva. http://www.who.int/uv/publications/globalindex/en/ or http://uv.biospherical.com/Solar_Index_Guide.pdf.

P. Kiedron, S. Stierle and K. Lantz (2007) Instantaneous UV Index and Daily UV Dose Calculations. NOAA-EPA Brewer Network. http://www.esrl.noaa.gov/gmd/grad/neubrew/docs/UVindex.pdf

Examples

UVI(sun.spct)
UVI(sun.spct, "WMO")
round(UVI(sun.spct), 0)