Methods for substituting onsite ambient ultraviolet radiation measurements for personal exposure studies

Measurements of personal ultraviolet radiation (UVR) exposure are a helpful tool in estimating people's UVR exposure. Gained values are valid for the corresponding location, time and date only. Assessment of personal UVR exposure as well as its translation to other locations, times and dates require ambient UVR as a reference. In some cases, UVR measurements are not available at the study site for practical reasons. Therefore, we have investigated alternative methods to substitute on-site measurements of ambient erythemally weighted daily radiant exposure. These methods comprise the assumption of spatial persistency of measurements from distant high-grade instruments, model calculations including clouds (TEMIS) and satellite measurements (OMI). Evaluation was done by substituting measurements of a high-grade instrument operated in Vienna, Austria. Our results show that up to a distance of 82 km the assumption of spatial persistency delivers lowest uncertainties. For larger distances, TEMIS performs better. Substituting with OMI carries the highest uncertainty but is the only method with global coverage, and therefore the only applicable method in large parts of the world. For correction of altitude, an increase of +14%/1000 m was found for clear sky, but for all-sky, monthly medians up to +40%/1000 m were found.