Uvb surface albedo measurements using biometers

Abstract

ABSTRACT. This work describes ultraviolet-B albedo measurements performed over several surfaces and different atmospheric conditions. These results provide a complement to previous studies as Blumthaler & Ambach (1988), widely used as albedo reference for the main UV radiative transfer models. A custom-built albedometer composed of a pair of Solarlight UVB501 biometer was used to measure the albedo over the following surfaces: green and yellowish grass, sand, wood (natural and painted), formica (synthetic plate), and iron. Influence of clouds and the sensor's response to temperature variations are also discussed. Presence of clouds on surface albedo measurement seems negligible, but a thermo-regulated instrument is indispensable to an accurate analysis. Comparison with previous works shows the need for studies on the detailed characterization of the type of surface.Keywords: surface albedo, ultraviolet radiation, radiative transfer models. RESUMO.Este trabalho apresenta medidas de albedo UVB realizadas sobre diferentes tipos de superfície e condições atmosféricas. Tais resultados fornecem uma contribuição a trabalhos prévios, tais como Blumthaler & Ambach (1988) amplamente utilizado em modelos de transferência radiativa. Para tanto, um albedômetro foi construído a partir de dois biômetros Solarlight UVB501 e as medidas foram realizadas sobre as seguintes superfícies: grama verde e amarelada, areia, madeira (natural e pintada), fórmica e metal. Ao contrário de outras publicações sobre o assunto, a influência de nuvens e a resposta do sensoràs variações de temperatura foram discutidas com maior profundidade. Verificou-se, que as nuvens não exercem influência significativa sobre a determinação do albedo, enquanto o uso de sensores termo reguladosé imprescindível para a obtenção de medidas precisas. Além disso, o trabalho demonstra a necessidade da realização de estudos que detalhem as superfícies estudadas de maneira mais aprofundada.Palavras-chave: albedo de superfície, radiação ultravioleta, modelos de transferência de radiação.

Ultraviolet Radiation Albedo and Reflectance in Review: The Influence to Ultraviolet Exposure in Occupational Settings

“…Table 2 provides a list of published broadband albedo or reflectance measurements [ 14 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 ], based upon measurements made with the sun as the main source of irradiance, except in one or two instances where an artificial UV source has been used. The identification number of each publication in Table 2 is used in Table 3 and Table 4 .…”

“…Extra description for each surface does not necessarily mean that comparisons can be made easily. Grass albedo measurements show that it is the composition of the surface that is the factor that causes variation in albedo measurement as is shown by [ 25 , 26 ] where Diffey et al, shows variation in grass albedo from different countries, while Correa and Ceballos show the difference in green and yellow grass albedo. These contrast strongly with the assumptions made by Coakley [ 9 ] which suggests the assumptions are not appropriate to be incorporated even for localised UV albedo.…”

Solar ultraviolet radiation: properties, characteristics and amounts observed in Brazil and South America

“…Finally, the ability of the surface to reflect UV-R should also be considered. Surfaces like grass, sand and asphalt reflect between 1 and 5%, while surfaces painted white or finer sand can reflect up to 10% of the incident UV-R. On the other hand, snow has a high reflectance in the UV spectrum; in case of dry and fresh snow it may reflect more than 90% of the incident UV-R. 22 , 23 For this reason solar protection, mainly wearing sunglasses, is highly recommended to those facing exposure in snowy regions.…”

Effective cloud optical depth for overcast conditions determined with a UV radiometers

“…On the basis of maps and satellite data, the percentage of rural land (fields, crops and grassland) was estimated to be 60% while urban land (asphalt roads, tar roofs and concrete) account for the remaining 40%. Published estimates for UVB albedos (Blumthaler and Ambach, ; Feister and Grewe, ; McKenzie and Kotkamp, ; Castro et al , ; Chadysiene and Girgzdys, ; Correa and Ceballos, ) give a much lower value for rural as compared to urban surfaces. Averaging all rural estimates, a figure of 1.9(±1.2)% was obtained as compared to 8.2(±2.8)% for urban land.…”