The success of the Montreal Protocol in curbing increases in harmful solar ultraviolet (UV) radiation at the Earth’s surface has recently been demonstrated. This study also provided evidence that the UV Index (UVI) measured by SUV-100 spectroradiometers at three Antarctic sites (South Pole, Arrival Heights, and Palmer Station) is now decreasing. For example, a significant (95% confidence level) downward trend of −5.5% per decade was reported at Arrival Heights for summer (December through February). However, it was also noted that these measurements are potentially affected by long-term drifts in calibrations of approximately 1% per decade. To address this issue, we have reviewed the chain of calibrations implemented at the three sites between 1996 and 2018 and applied corrections for changes in the scales of spectral irradiance (SoSI) that have occurred over this period (Method 1). This analysis resulted in an upward correction of UVI data measured after 2012 by 1.7% to 1.8%, plus smaller adjustments for several shorter periods. In addition, we have compared measurements during clear skies with model calculations to identify and correct anomalies in the measurements (Method 2). Corrections from both methods reduced decadal trends in UVI on average by 1.7% at the South Pole, 2.1% at Arrival Heights, and 1.6% at Palmer Station. Trends in UVI calculated from the corrected dataset are consistent with concomitant trends in ozone. The decadal trend in UVI calculated from the corrected dataset for summer at Arrival Heights is −3.3% and is significant at the 90% level. Analysis of spectral irradiance measurements at 340 nm suggests that this trend is partially caused by changes in sea ice cover adjacent to the station. For the South Pole, a significant (95% level) trend in UVI of −3.9% per decade was derived for January. This trend can partly be explained by a significant positive trend in total ozone of about 3% per decade, which was calculated from SUV-100 and Dobson measurements. Our study provides further evidence that UVIs are now decreasing in Antarctica during summer months. Reductions have not yet emerged during spring when the ozone hole leads to large UVI variability.

中文翻译：

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南极紫外线辐射的趋势

最近已证明《蒙特利尔议定书》在遏制地球表面有害的紫外线（UV）辐射增加方面取得了成功。这项研究还提供了证据，表明通过SUV-100分光光度计在三个南极站点（南极，到达高度和帕尔默站）测量的UV指数（UVI）现在正在降低。例如，据报道，夏季（12月至2月）到达高度达到每十年显着下降（95％的置信水平）-5.5％的趋势。但是，还应注意，这些测量值可能受到校准的长期漂移（每十年约1％）的影响。为了解决这个问题，我们回顾了1996年至2018年在这三个站点实施的一系列校准，并对这一时期发生的光谱辐照度（SoSI）的变化进行了校正（方法1）。这项分析导致2012年之后测得的UVI数据向上修正了1.7％至1.8％，并对几个较短的时期进行了较小的调整。此外，我们将晴朗天空中的测量值与模型计算进行了比较，以识别和纠正测量值中的异常（方法2）。两种方法的修正均使南极的UVI年代际趋势平均降低了1.7％，到达高度的平均降低了2.1％，而帕默站的降低了1.6％。根据校正后的数据集计算出的UVI趋势与臭氧的伴随趋势一致。根据校正后的夏季到达高度数据集得出的UVI的十年趋势为-3.3％，在90％的水平上显着。对340 nm处的光谱辐照度测量值的分析表明，这种趋势部分是由邻近气象站的海冰覆盖变化引起的。对于南极而言，1月份的UVI显着（95％水平）趋势为每十年-3.9％。这种趋势可以部分解释为臭氧总量的显着正趋势，即每十年大约3％，这是通过SUV-100和Dobson测量得出的。我们的研究提供了进一步的证据，表明夏季夏季南极洲的紫外线含量正在下降。在春季，当臭氧孔导致较大的UVI变化时，还没有出现减少的趋势。对340 nm处的光谱辐照度测量值的分析表明，这种趋势部分是由邻近气象站的海冰覆盖变化引起的。对于南极而言，一月份的UVI趋势为每十年−3.9％的显着趋势（95％）。这种趋势可以部分解释为臭氧总量的显着正趋势，即每十年大约3％，这是通过SUV-100和Dobson测量得出的。我们的研究提供了进一步的证据，表明夏季夏季南极洲的紫外线含量正在下降。当臭氧孔导致较大的UVI变化时，春季还没有减少。对340 nm处的光谱辐照度测量值的分析表明，这种趋势部分是由邻近气象站的海冰覆盖变化引起的。对于南极而言，一月份的UVI趋势为每十年−3.9％的显着趋势（95％）。这种趋势可以部分解释为臭氧总量的显着正趋势，即每十年大约3％，这是通过SUV-100和Dobson测量得出的。我们的研究提供了进一步的证据，表明夏季夏季南极洲的紫外线含量正在下降。在春季，当臭氧孔导致较大的UVI变化时，还没有出现减少的趋势。这种趋势可以部分解释为臭氧总量的显着正趋势，即每十年大约3％，这是通过SUV-100和Dobson测量得出的。我们的研究提供了进一步的证据，表明夏季夏季南极洲的紫外线含量正在下降。在春季，当臭氧孔导致较大的UVI变化时，还没有出现减少的趋势。这种趋势可以部分解释为臭氧总量的显着正趋势，即每十年大约3％，这是通过SUV-100和Dobson测量得出的。我们的研究提供了进一步的证据，表明夏季夏季南极洲的紫外线含量正在下降。在春季，当臭氧孔导致较大的UVI变化时，还没有出现减少的趋势。