Characteristics of Ultraviolet Radiation in the Human Erythema Band Measured with a Robertson-Berger Meter and a Double Monochromator

摘要

In an in-depth analysis, data from a Robertson-Berger (RB) erythema flux meter were compared with concurrent measurements obtained with an ultraviolet spectroradiometer and with theoretically calculated uv fluxes. The absolute energy of one sunburn unit measured by the RB-meter was determined. It was found that at a solar zenith angle of 30 degrees one sunburn unit (SU) is equivalent to 35 + or - 4 mJ per sq cm, and at a solar zenith angle of 69 degrees one SU is equivalent to 20 + or - 2 mJ per sq cm (relative to a wavelength of 297 nm), where the rate of change is nonlinear. The difference is due to the RB-meter's imperfect simulation of the response of human skin to the incident uv solar spectrum. Moreover, the rate of growth of the deviation with increasing solar zenith angle was found to be 1.2% per degree between solar zenith angles 30 degree to 50 degree and 2.3% per degree between solar zenith angles 50 degree to 70 degree. These deviations of response with solar zenith angle were found to be consistent with reported RB-meter characteristics. Also given are examples of relative errors in RB-meter data due to latitude and seasonal variations in solar zenith angle.