Joanna Turner

Reflected solar radiation from horizontal, vertical and inclined surfaces: Ultraviolet and visible spectral and broadband behaviour due to solar zenith angle, orientation and surface type

Ultraviolet (UV) radiation affects human life and UV exposure is a significant everyday factor that individuals must be aware of to ensure minimal damaging biological effects to themselves. UV exposure is affected by many complex factors. Albedo is one factor, involving reflection from flat surfaces. Albedo is defined as the ratio of reflected (upwelling) irradiance to incident (downwelling) irradiance and is generally accepted only for horizontal surfaces. Incident irradiance on a non horizontal surface from a variety of incident angles may cause the reflectivity to change. Assumptions about the reflectivity of a vertical surface are frequently made for a variety of purposes but are rarely quantified. As urban structures are dominated by vertical surfaces, using albedo to estimate influence on UV exposure is limiting when incident (downwelling) irradiance is not normal to the surface. Changes to the incident angle are affected by the solar zenith angle, surface position and orientation and surface type. A new characteristic describing reflection from a surface has been used in this research. The ratio of reflected irradiance (from any surface position of vertical, horizontal or inclined) to global (or downwelling) irradiance (RRG) has been calculated for a variety of metal building surfaces in winter time in the southern hemisphere for both the UV and visible radiation spectrum, with special attention to RRG in the UV spectrum. The results show that the RRG due to a vertical surface can exceed the RRG due to a horizontal surface, at smaller solar zenith angles as well as large solar zenith angles. The RRG shows variability in reflective capacities of surface according to the above mentioned factors and present a more realistic influence on UV exposure than albedo for future investigations. Errors in measuring the RRG at large solar zenith angles are explored, which equally highlights the errors in albedo measurement at large solar zenith angles.

Measurements of the upper body ultraviolet exposure to golfers: non‐melanoma skin cancer risk, and the potential benefits of exposure to sunlight

Background: Geographically, Queensland presents an extreme ultraviolet exposure climate to members of the public engaged in outdoor recreational activity. The risk of developing a skin cancer or an eye disease as a result of incidental exposure to naturally occurring ultraviolet radiation in the outdoor environment is proportionately high in a Queensland population compared with fair‐skinned population groups residing in comparable Northern Hemisphere latitudes. In contrast to these risks, elderly members of this high growth population group have been reported to be vitamin D deficient. The risks and potential benefits of exposure to sunlight in southern Queensland are assessed in this study with respect to recreational golfing. This sport is a popular recreational activity for the Queensland population and must be played during daylight hours.

Ultraviolet Reflection Irradiances and Exposures in The Constructed Environment For Horizontal, Vertical and Inclined Surfaces

Ultraviolet (UV) reflection in the urban constructed environment is not well understood for topical issues such as measuring and modeling the received UV exposure due to that UV reflection for outdoor workers. Both predominantly specular and diffuse reflecting surface types have been identified and investigated for the erythemal UV reflection ratio variation due to solar zenith angle and orientation. This paper presents relationships between erythemal UV reflection ratios measured for non‐horizontal and horizontal surfaces, with predominantly specular surface types indicating stronger relationships with solar zenith angles than diffuse reflecting surfaces types. Erythemal UV exposures caused by the same reflecting surface types at three inclinations are also investigated. Non‐horizontal surfaces can increase erythemal UV exposures compared to erythemal UV exposures received from the same horizontal surface by factors of 1.07–1.46 for specific body sites and by 1.01–1.70 for averages of group body sites for zinc aluminium coated steel sheeting.

Solar UV exposures measured simultaneously to all arbitrarily oriented leaves on a plant

The possible ramifications of climate change include the influence it has upon the amount of cloud cover in the atmosphere. Clouds cause significant variation in the solar UV radiation reaching the earths surface and in turn the amount incident on ecosystems. The consequences of changes in solar UV radiation delivered to ecosystems due to climate change may be significant and should be investigated. Plants are an integral part of the world wide ecological balance, and research has shown they are affected by variations in solar UV radiation. Therefore research into the influence of solar UV radiation on plants is of particular significance. However, this requires a means of obtaining detailed information on the solar UV radiation received by plants. This research describes a newly developed dosimetric technique employed to gather information on solar UV radiation incident to the leaves of plants in combination with the measurement of spectral irradiances in order to provide an accurate method of collecting detailed information on the solar UV radiation affecting the canopy and lower leaf layers of individual plants. Variations in the measurements take into account the inclination and orientation of each leaf investigated, as well as the influence of shading by other leaves in the plant canopy.

Comparison of biologically effective spectra for erythema and pre-vitamin D3 synthesis

The short wavelength cut-off (λc), the wavelength of the maximum spectral UV (λMax) of spectral pre-vitamin D3 effective solar UV irradiance (UVD3), and the spectral erythemal UV (UVEry) were compared at 5-min intervals over a 6-month period at solar zenith angles (SZA) ranging from 4.7° to 80°. Averaged over the entire period, λc for UVD3 is higher by 1.05 nm than that for UVEry. The λMax is higher for UVD3 compared to UVEry for SZA < ~50°. For higher SZA (>55°), the ratio of λMax for UVD3 to that for UVEry is less than 1. As the erythemal action spectrum extends into the UVA, the ratio of UVD3 to UVEry irradiances decreases with increasing SZA, along with a decrease in the ratio of λMax for UVD3 compared to UVEry. The changes in λc and λMax influence both personal UVD3 and UVEry exposure and, to take this into account, a dual calibration technique for polysulphone dosimeters has been developed to simultaneously provide measurements of both types of exposure.

Variations in the short wavelength cut-off of the solar UV spectra

Cloud and solar zenith angle (SZA) are two major factors that influence the magnitude of the biologically damaging UV (UVBD) irradiances for humans. However, the effect on the short wavelength cut-off due to SZA and due to clouds has not been investigated for biologically damaging UV for cataracts. This research aims to investigate the influence of cloud and SZA on the short wavelength cut-off of the spectral UVBD for cataracts. The spectral biologically damaging UV for cataracts on a horizontal plane was calculated by weighting the spectral UV measured with a spectroradiometer with the action spectrum for the induction of cataracts in a porcine lens. The UV spectra were obtained on an unshaded plane at a latitude of 29.5 degrees S. The cut-off wavelength (lambdac) was defined as the wavelength at which the biologically damaging spectral irradiance was 0.1% of the maximum biologically damaging irradiance for that scan. For the all sky conditions, the short wavelength cut-off ranged by 12 nm for the SZA range of 5 to 80 degrees and the maximum in the spectral UVBD ranged by 15 nm. Similarly, for the cloud free cases, the short wavelength cut-off ranged by 9 nm for the same SZA range. Although, cloud has a large influence on the magnitude of the biologically damaging UV for cataracts, the influence of cloud on the short wavelength cut-off for the biologically damaging UV for cataracts is less than the influence of the solar zenith angle.

Characterisation of a smartphone image sensor response to direct solar 305 nm irradiation at high air masses

This research reports the first time the sensitivity, properties and response of a smartphone image sensor that has been used to characterise the photobiologically important direct UVB solar irradiances at 305nm in clear sky conditions at high air masses. Solar images taken from Autumn to Spring were analysed using a custom Python script, written to develop and apply an adaptive threshold to mitigate the effects of both noise and hot-pixel aberrations in the images. The images were taken in an unobstructed area, observing from a solar zenith angle as high as 84° (air mass=9.6) to local solar maximum (up to a solar zenith angle of 23°) to fully develop the calibration model in temperatures that varied from 2°C to 24°C. The mean ozone thickness throughout all observations was 281±18 DU (to 2 standard deviations). A Langley Plot was used to confirm that there were constant atmospheric conditions throughout the observations. The quadratic calibration model developed has a strong correlation between the red colour channel from the smartphone with the Microtops measurements of the direct sun 305nm UV, with a coefficient of determination of 0.998 and very low standard errors. Validation of the model verified the robustness of the method and the model, with an average discrepancy of only 5% between smartphone derived and Microtops observed direct solar irradiances at 305nm. The results demonstrate the effectiveness of using the smartphone image sensor as a means to measure photobiologically important solar UVB radiation. The use of ubiquitous portable technologies, such as smartphones and laptop computers to perform data collection and analysis of solar UVB observations is an example of how scientific investigations can be performed by citizen science based individuals and groups, communities and schools.

Improved method of ultraviolet radiation reflection measurement for non-horizontal urban surfaces

The technique of ultraviolet reflection ratio measurement is modified from the traditional albedo measurement in order to compensate for unusual inflation of the reflection ratio found previously in non-horizontal surface ultraviolet reflection studies. Data collected to test this method of reflection ratio collection show that there is significant reduction in the inflation. In order to collect UV reflection ratio data on non-horizontal surfaces that can be comparable to differently oriented planar surfaces, the sun and the sensors positions during the measurement process are equally important, which leads to this new method of reflection measurement for non-horizontal surfaces.

Detection of ultraviolet B radiation with internal smartphone sensors

ABSTRACT Smartphones have the potential to monitor ultraviolet radiation within the terrestrial solar spectrum. Additionally, the ability to accurately estimate personal ultraviolet exposure using a smartphone may one day allow an individual control of their ultraviolet exposure. Previous studies have demonstrated the detection of ultraviolet A from 320 to 400 nm with a smartphone. However, the measurement of ultraviolet B from 280 to 320 nm is desirable to monitor biological effects such as erythema. No previous reports have been reported for the detection of ultraviolet B detection with a smartphone camera. This study characterized the ultraviolet B response of smartphone cameras and shows that these devices detect this radiation without additional hardware. Three smartphones were tested in the ultraviolet B waveband for dark response, temperature response, irradiance response, and spectral response. The used protocols adhered to international standards where applicable. All characterized smartphones were sensitive to ultraviolet B radiation; however, each type provides a unique response.

Minimum Exposure Limits and Measured Relationships Between the Vitamin D, Erythema and International Commission on Non-Ionizing Radiation Protection Solar Ultraviolet

The International Commission on Non‐Ionizing Radiation Protection (ICNIRP) has established guidelines for exposure to ultraviolet radiation in outdoor occupational settings. Spectrally weighted ICNIRP ultraviolet exposures received by the skin or eye in an 8 h period are limited to 30 J m−2. In this study, the time required to reach the ICNIRP exposure limit was measured daily in 10 min intervals upon a horizontal plane at a subtropical Australian latitude over a full year and compared with the effective Vitamin D dose received to one‐quarter of the available skin surface area for all six Fitzpatrick skin types. The comparison of measured solar ultraviolet exposures for the full range of sky conditions in the 2009 measurement period, including a major September continental dust event, show a clear relationship between the weighted ICNIRP and the effective vitamin D dose. Our results show that the horizontal plane ICNIRP ultraviolet exposure may be used under these conditions to provide minimum guidelines for the healthy moderation of vitamin D, scalable to each of the six Fitzpatrick skin types.