Moise A F, Aynsley R
School of Mathematics, Computer Sciences and Physics, James Cook University, Townsville, Queensland, Australia.
Int J Biometeorol. 1999 Nov;43(3):128-38. doi: 10.1007/s004840050128.
As people become better informed about the harmful effects of prolonged exposure to solar ultraviolet radiation (UVR, 280-400 nm) they will seek the protection of shade, particularly in tropical locations such as Townsville (19 degrees south). Using broad-band radiation sensors for solar ultraviolet-B (280-315 nm), ultraviolet-A (315-400 nm) and daylight (400-800 nm) radiation, the exposure levels were measured in both the horizontal (shaded and unshaded) and vertical (shaded and unshaded) directions. The measurements were conducted at eight locations (shade settings) in Townsville during the period between December 1997 (summer) and May 1998 (beginning of winter). The quality of protection was assessed by the ratio of unshaded to shaded radiation exposure, the UVB/shade protection ratio (UVB-SPR). The UVB-SPR varies considerably between the different shade settings, with a beach umbrella showing the least protection and dense foliage the highest protection. The roof of a house verandah can provide only little protection if the verandah catches the afternoon sun. Increasing cloud cover decreases the UVB-SPR for all settings because of the increase in the diffuse fraction of the radiation. Only one setting provided a UVB-SPR of 15 or higher, as suggested for protective shading against solar UVB radiation. Shade from direct sunlight alone does not provide enough protection against high levels of solar UVR. Apart from the transmission qualities of the shading material, it is the construction of the whole shade setting that determines the exposure levels underneath. A shade structure with enough overhang is recommended so that high levels of scattered radiation do not reach the skin.
随着人们对长期暴露于太阳紫外线辐射（UVR，280 - 400纳米）的有害影响有了更深入的了解，他们会寻求阴凉处的庇护，尤其是在像汤斯维尔（南纬19度）这样的热带地区。使用宽带辐射传感器测量太阳紫外线B（280 - 315纳米）、紫外线A（315 - 400纳米）和日光（400 - 800纳米）辐射，在水平（有阴影和无阴影）和垂直（有阴影和无阴影）方向上测量了暴露水平。测量于1997年12月（夏季）至1998年5月（冬季开始）期间在汤斯维尔的八个地点（遮阳设置）进行。通过无阴影与有阴影辐射暴露的比率，即UVB/遮阳保护率（UVB - SPR）来评估保护质量。不同遮阳设置下的UVB - SPR差异很大，沙滩伞提供的保护最少，茂密的树叶提供的保护最高。如果阳台在下午能晒到太阳，房屋阳台的屋顶只能提供很少的保护。云层增加会降低所有设置下的UVB - SPR，因为辐射的漫射部分增加了。只有一种设置提供了15或更高的UVB - SPR，这是针对防止太阳UVB辐射的保护性遮阳所建议的。仅靠直射阳光的阴影并不能提供足够的保护以抵御高水平的太阳UVR。除了遮阳材料的透射特性外，整个遮阳设置的结构才决定了下面的暴露水平。建议使用有足够悬挑的遮阳结构，这样高水平的散射辐射就不会到达皮肤。
