A Variable Sky-View Platform for the Measurement of Ultraviolet Radiation

Abstract

One of the more difficult tasks confronting atmospheric researchers today is the acquisition of long-term radiometric measurements that encapsulate variability in the sky hemisphere as well as time. High quality spatial measurements would allow for a greater understanding of atmospheric processes, both specific to the site and between locations. This information would lead to further development of better spatial models for predicting future trends. This study develops a timer-controlled variable sky-view platform (VSP), designed to encapsulate both the spatial and temporal variation of radiation in the sky hemisphere for Hobart, Australia (42.90ЊS, 147.33ЊE). The VSP essentially allows for a sensor to move up and down inside a fixed cylinder, therefore causing the skyview factor to vary. A full description of the VSP design, electronics, and construction is given. Emphasis is on high-precision long-term operation under all weather conditions. A modeling scheme and output results illustrate the advantages of the VSP over current sky-observing instruments. It can accurately parameterize the direct and diffuse erythemal irradiance as well as the azimuthally integrated erythemal sky radiance distribution for every 2-min duration (at the current setting). In addition, all data can be obtained for clear-sky and cloudy conditions. The VSP is currently in use with the erythemal ultraviolet (UV) biometer 501-A manufactured by Solar Light Company, Inc. (SLC). As such, it provides an additional source of UV sky distribution data to the Hobart UVclimatology database.

Modeling and measurements of UV-B irradiance in cloudy conditions

“…This configuration also allows direct and diffuse spectral irradiance to be extracted from one single instrument platform. Further instrument details and quality control ar e described in Kuchinke (2002) and Kuchinke and Nunez (2002).…”

Modelling ultraviolet exposures in a school environment

“…Often however, the influence of the surrounding environment is neglected, due to the time required, and difficulties in making accurate environmental measurements sufficient to detail all the factors that impact ambient UV. The influence of solar position and its effect on surface albedo 2,3 , variation with sky view 4 , and surface inclination 5,6 have each been investigated and modelled in past research, however no mechanism has yet been developed to take each of these factors into account to model horizontal plane damaging UV in a realistic environment. Additionally, horizontal plane damaging UV does not accurately represent exposure likely to be incident on exposed surfaces of the human body although many studies have been and continue to be conducted to investigate and model this effect.…”