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

Abstract

To investigate the angular distributions of UVA, UVB, and effective UV for erythema and vitamin D (vitD) synthesis, the UV spectral irradiances were measured at ten inclined angles (from 0° to 90°) and seven azimuths (from 0° to 180°) at solar elevation angle (SEA) that ranged from 18.8° to 80° in Shanghai (31.22° N, 121.55° E) under clear sky and the albedo of ground was 0.1. The results demonstrated that in the mean azimuths and with the back to the sun, the UVA, UVB, and erythemally and vitD-weighted irradiances increased with the inclined angles and an increase in SEA. When facing toward the sun at 0°-60° inclined angles, the UVA first increased and then decreased with an increase in SEA; at other inclined angles, the UVA increased with SEA. At 0°-40° inclined angles, the UVB and erythemally and vitD-weighted irradiances first increased and then decreased with an increase in SEA, and their maximums were achieved at SEA 68.7°; at other inclined angles, the above three irradiances increased with an increase in SEA. The maximum UVA, UVB, and erythemally and vitD-weighted irradiances were achieved at an 80° inclined angle at SEA 80° (the highest in our measurements); the cumulative exposure of the half day achieved the maximum at a 60° inclined angle, but not on the horizontal. This study provides support for the assessment of human skin sun exposure.

The Relationship Between PM2.5 and the Action Spectrum of Ultraviolet Radiation for Vitamin D Production Based on a Manikin Model

“…Moreover, the UV radiation intensity received by the human body was reflected by the UV radiation intensity at different inclination angles. This homemade multiangle ultraviolet radiation monitoring model was also applied in our previous study [41]. After monitoring the ultraviolet radiation intensity received under different inclination angles under different concentrations of PM 2.5 , multiple linear regression modeling was performed to better reflect the relationship between UV vitD and the SEA, PM 2.5 , and inclination angle.…”

“…A shelf was fixed on the tripod head, and the detectors were placed in front of the shelf. We also used these experimental instruments in a previous study [41].…”

Determining an Effective UV Radiation Exposure Time for Vitamin D Synthesis in the Skin Without Risk to Health: Simplified Estimations from UV Observations

“…Liu et al . analyzed the angular distribution of UV irradiated on a surface inclined from 0 to 90° at every solar elevation angle (SEA, ~80°) and azimuthal angle (~180°) under a clear sky by taking spectral UV measurements corresponding to UV Ery and UV VitD irradiated on an area of skin that was not always horizontal. For example, for a 10° incline of the skin toward the sun and a low SEA of 18.8°, the UV VitD would be 2.7 times higher than that on a horizontal plane, and for a 30° incline, it would be 1.59 times higher at a SEA of 29.4°.…”

Ground-based measurements of the weather-driven sky radiance distribution in the Southern Hemisphere

“…By definition, the diffuse irradiance of a sloping plane can be calculated by integrating the radiance distribution of the sky 'seen' by the plane [1]. Reliable information on the sky-diffuse radiance distribution enables better estimations of the power output of photovoltaic (PV) modules [2][3][4][5], the energy production potential of tilted surfaces and building fac ¸ades [6,7], and the ultraviolet (UV) doses on humans [8][9][10].…”