McKenzie Richard, Bodeker Greg, Scott Gwen, Slusser Jim, Lantz Kathleen
National Institute of Water & Atmospheric Research, NIWA Lauder, Central Otago, New Zealand.
Photochem Photobiol Sci. 2006 Mar;5(3):343-52. doi: 10.1039/b510943d. Epub 2006 Jan 23.
UV measurements from instruments maintained by USDA at 16 mid-latitude sites were analysed to investigate geographic differences. Fifteen of the sites are in North America, and one is in New Zealand. The instruments measure erythemally weighted UV radiation, and the results are presented in terms of UV Index (UVI). The focus of this work is on data from 2003, but the main results are also shown for years 2002 and 2004. In the North American sites, the peak UVI values increase by approximately 15% between latitudes 47 degrees N and 40 degrees N, and they show an increase with altitude of approximately 15% in the first kilometer, but much smaller rates of increase above that level. Peak UV intensities in the New Zealand site (45 degrees S, alt. 0.37 km) exceed those at comparable latitudes and altitudes in North America by 41 +/- 5%, and are more comparable with those over 1 km higher and 5 degrees closer to the equator. The number of observations on these days that exceeded various thresholds of UVI showed similar patterns. Furthermore, the number of days in which the peak values exceeded various thresholds also showed similar patterns, with the number of extreme values in New Zealand being anomalously high. For example, the only sites in North America where UVI exceeded 12 were at the high altitude sites in Colorado and Utah, for which there were 53 days, 6 days and 2 days respectively at the 3.2 km, 1.6 and 1.4 km sites. By contrast, the peak UVI at Lauder (0.37 km) exceeded 12 on 17 days. Lauder was the only site under 1 km altitude where the UVI exceeded 11 on a regular basis (48 days). The optical depths at Lauder were significantly lower than at all North American sites. These, together with the lower ozone amounts and the closer Earth-Sun separation in summer all contribute to the relatively high UV intensities at the New Zealand site. Other sites in New Zealand show similar increases compared with corresponding sites in North America, and the differences persist from year to year. The contrast in UV between New Zealand and North America is similar to that observed previously between New Zealand and Europe. During winter months, the UVI in New Zealand is not particularly high, giving a larger summer/winter contrast in UVI, which may be important from a health perspective.
对美国农业部在16个中纬度站点所维护仪器的紫外线测量数据进行了分析，以研究地理差异。其中15个站点位于北美洲，1个站点位于新西兰。这些仪器测量红斑加权紫外线辐射，并以紫外线指数（UVI）呈现结果。这项工作的重点是2003年的数据，但也给出了2002年和2004年的主要结果。在北美洲的站点，紫外线指数峰值在北纬47度至40度之间增加了约15%，在海拔每升高1公里时，紫外线指数峰值增加约15%，但在该高度以上增加速率要小得多。新西兰站点（南纬45度，海拔0.37公里）的紫外线峰值强度比北美洲类似纬度和海拔的站点高出41±5%，与北美洲海拔高出1公里且纬度更靠近赤道5度的站点更为接近。这些日子里超过不同紫外线指数阈值的观测次数呈现出类似模式。此外，紫外线峰值超过不同阈值的天数也呈现出类似模式，新西兰的极值天数异常高。例如，北美洲紫外线指数超过12的站点仅位于科罗拉多州和犹他州的高海拔站点，在海拔3.2公里、1.6公里和1.4公里的站点，分别有53天、6天和2天紫外线指数超过12。相比之下，劳德（海拔0.37公里）的紫外线峰值在17天超过12。劳德是海拔低于1公里且紫外线指数经常超过11（48天）的唯一站点。劳德的光学厚度明显低于所有北美洲站点。这些因素，再加上较低的臭氧量以及夏季地球与太阳距离更近，都导致了新西兰站点相对较高的紫外线强度。新西兰的其他站点与北美洲相应站点相比也有类似的增加，且这种差异逐年持续。新西兰和北美洲之间紫外线的差异与之前在新西兰和欧洲之间观察到的类似。在冬季月份，新西兰的紫外线指数不是特别高，这使得紫外线指数在夏季和冬季的对比更大，从健康角度来看这可能很重要。
