Measurements of UV radiation on rotating vertical plane at the ALOMAR Observatory (69° N, 16° E), Norway, June 2007

Abstract

Abstract. Erythemaly weighted UV and total UV-A irradiance measured at the ALOMAR (Arctic Lidar Observatory for Middle Atmosphere Research; 69 • N, 16 • E) in June 2007 by two Kipp & Zonen UV broadband meters type, UV-S-EA-T, are examined. One unit is mounted on rotating vertical plane and the other is permanently fixed horizontally. The UV broadband meters measure simultaneously to compare UV irradiances on vertical and horizontal planes. The entire range of such relative exposure variations during clearsky and overcast conditions over ALOMAR in the period March-June 2007 is examined using STAR and Radonic1 model (developed at the Meteorological Institute, University of Munich) for various action spectra: erythema, UV-A, and vitamin D 3 . The model and observations support that the daily means of relative exposures are quite stable, i.e., vary within the range 0.4-0.6 with the mean around 0.5 when the averaged intra-day, day-to-day, and seasonal changes of the relative erythemal exposures are considered. It seems that multiplication of the daily mean dose from a broadband meter placed horizontally by the factor of 0.5 gives reasonable estimation of the daily mean exposure on a vertically oriented receiver randomly oriented towards the Sun. The model studies during clear-sky conditions show that the extreme value and daily variability of relative exposure are the highest for UV-A, next for erythemal UV, then for vitamin D 3 weighed UV irradiance. The minima of relative exposure (∼0.20-0.30) are almost the same for all weighting functions. The comparison of model simulations and measurements suggests that specific cloud configuration could lead to significant enhancement of UV exposure of rotating receiver.

Solar UV Geometric Conversion Factors: Horizontal Plane to Cylinder Model†

“…2-1.3, in agreement with Wester and Jossefssons's (16) calculated maximum ratio of 1.2 for a sloped plane and with Stick et al's (17) maximum ratio of 1.3 for an inclined cylinder. Our data for sloped planes with various orientations are within 1.1% of the calculations of Koepke and Mech(3), who performed in-depth modeling of irradiance on arbitrarily oriented surfaces, and both the simulations and actual measurements of Sobolewski et al(9). They got vertical plane ratio minima of about 0.2 for 0°SZA and vertical plane ratio maxima of about 0.9 for >70°SZA.…”

“…Converting irradiances on a horizontal plane to irradiances closer to what people get while they are outdoors has not been solved using simple geometric shapes, such as cylinders, in a universally applicable manner (5)(6)(7)(8)(9). For example, Sobolewski et al (9) developed vertical rotating two-dimensional planes while Hoeppe et al (10) developed a complex, virtual three-dimensional wireframe human body surface model, and Streicher et al (7) developed a novel modification of ray tracing algorithms to produce ''patches'' of polygons representing anatomical regions on the human body. While those sophisticated models have other useful applications, such as identifying specific areas at risk for UV doses higher than the horizontal plane, they have not been used to convert horizontal plane doses to average cylindrical surface doses relevant to the complete human form.…”

Validation of modeled daily erythemal exposure along tropical and subtropical shipping routes by ship‐based and satellite‐based measurements

“…The average ratios of erythemal exposure between chest (back) and horizontal incidence of about 0.24 measured along the four tropical and subtropical routes are remarkably smaller than ratios reported in the literature from other experiments. For example, measurements by an azimuthally rotating UV radiometer performed in Norway in June at 69°N show ratios of erythemal radiation between vertical and horizontal incidence of 0.6 (0.4 to 0.8) for cloudless sky and about 0.45 for cloudy sky [Sobolewski et al, 2008]. Minimum SZAs at that place may have reached about 45.5°.…”

The angular distributions of ultraviolet spectral irradiance at different solar elevation angles under clear sky conditions

“…Humans partake in multiple activities outside, and the postures are random; therefore, the horizontal UVR cannot quantify the actual UVR exposure level of the human body. Based on these reasons, some researchers have investigated UVR using vertical angles because they could better account for the position of the eyes or some areas of the skin and subsequently compared these data with horizontal UVR (Webb et al 1999;Sobolewski et al 2008;Hu et al 2010b). Other researchers have measured UVR on inclined planes with fixed angles (Esteve et al 2006;Utrillas et al 2009;Navntoft et al 2012); Oppenrieder et al (2004Oppenrieder et al ( ), (2005 measured erythemally weighted UV irradiance at azimuth intervals of 15°on 0°and 45°inclined planes by the use of a fully automatic measuring system, an angle scanning radiometer.…”