Daily Surface UV Exposure and Its Relationship to Surface Pollutant Measurements

Abstract

For the past 30 years, the stratospheric ozone layer has decreased in the Northern Hemisphere. The main effect of this ozone decrease was an expected increase in the UV radiation at the Earth's surface, but there has been no clear evidence of an increasing urban trend in surface UV. This study shows that specific air pollutants can reduce the increased surface levels of UV radiation and offers an explanation for why the expected surface UV increases have not been observed, especially in urban regions.A U.S. Environmental Protection Agency (EPA) UV monitoring site at the University of California at Riverside combined with air pollution data from a site operated by the California Air Resources Board in Rubidoux, CA, provided the basis of this study. The 1997 South Coast Ozone Study (SCOS-97) provided three key ingredients: black carbon, PM 10 concentrations, and collocated radiometric measurements. The Total Ozone Mapping Spectrometer (TOMS) satellite data were used to provide the stratospheric ozone levels that were included in the statistical model. All of these input parameters would be used to test this study's hypothesis: the expected increase of surface UV radiation, caused by decreases in stratospheric ozone, can be masked by increases in anthropogenic emissions. The values for the pollutants were 7:00 a.m.-5:00 p.m. averages of the instrument's values taken during summer 1997.A statistical linear regression model was employed using the stratospheric ozone, black carbon, PM 10 , and surface ozone concentrations, and the sin (⌰) and cos (⌰). The angle ⌰ is defined by ⌰ ϭ 2 (Julian date/365). This model obtained a coefficient of determination of 0.94 with an uncertainty level (p value) of less than 0.3% for all of the variables in the model except ground-level ozone. The final model, regressed against a data set from a remote, western North Carolina site, resulted in a coefficient of determination of 0.92. The model shows that black carbon can reduce the Diffey-weighted UV levels that reach the surface by as much as 35%, depending on the season.

Aerosol single scattering albedo retrieved from measurements of surface UV irradiance and a radiative transfer model

“…It was found that DDR has little dependence on realistic values of TOC. In clear-sky periods, variations of tropospheric ozone do little to influence UV radiation, including its scattering, when compared to stratospheric ozone [Barnard et al, 2003]. Figure 3 shows that the sensitivity of DDR to w increased from AOD = 0.05 to AOD = 1.00, and this was also found to occur for g and ga. A further test was conducted to see how much a change in DDR of 0.02 would affect the retrieval of w as AOD is varied.…”

Comparison of UV irradiances from Aura/Ozone Monitoring Instrument (OMI) with Brewer measurements at El Arenosillo (Spain) – Part 1: Analysis of parameter influence

“…This wavelength dependence of OMI-Brewer bias for moderatehigh aerosol load may be partially attributed to the aerosol influence over the OMUVB products. Aerosols can also increase effective absorption path for tropospheric ozone and other anthropogenic gases causing more effective UV reduction at shorter UV wavelengths (Bernard et al, 2003;Kaskaoutis et al, 2006;Badarinath et al, 2007).…”

Risk Assessment of Face Skin Exposure to UV Irradiance from Different Rotation Angle Ranges

“…The API is a simple and generalized way to describe air quality, with a higher API corresponding to more serious air pollution. Some studies have shown that air pollution can reduce the surface levels of UV irradiance [39]. For both measuring days, (i) the mean API was approximately 62, (ii) the result of the diurnal variations of the ambient UVR irradiance were bell-shaped curves with peaks at approximately noon (approximately 12:00 CST, SEA 82°), and (iii) the ambient UVR irradiances were nearly the same for the two days.…”