Nadir-viewed intensities (radiances) from nine UV sensing satellite instruments are calibrated over the East Antarctic Plateau and Greenland during summer. The calibrated radiances from these UV instruments ultimately will provide a global long-term record of cloud trends and cloud response from ENSO events since 1980. We first remove the strong solar zenith angle dependence from the intensities using an empirical approach rather than a radiative transfer model. Then small multiplicative adjustments are made to these solar zenith angle normalized intensities in order to minimize differences when two or more instruments temporally overlap. While the calibrated intensities show a negligible long-term trend over Antarctica and a statistically insignificant UV albedo trend of −0.05 % per decade over the interior of Greenland, there are small episodic reductions in intensities which are often seen by multiple instruments. Three of these darkening events are explained by boreal forest. Other events are caused by surface melting or volcanoes. We estimate a 2-sigma uncertainty of 0.35 % for the calibrated radiances.

中文翻译：

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自1980年以来，在南极和格陵兰岛上对九种紫外线传感仪器进行了相互校准

在夏季，校准了来自南极高原和格陵兰岛上九种紫外线感应卫星仪器的最低点（辐射）。自1980年以来，这些紫外线仪器的校准辐射最终将提供全球云趋势和ENSO事件云响应的长期记录。我们首先使用经验方法而非辐射转移模型从强度中去除强烈的太阳天顶角依赖性。然后，对这些太阳天顶角归一化强度进行小的乘法调整，以最小化两个或多个仪器在时间上重叠时的差异。虽然校准后的强度在南极洲的长期趋势可忽略不计，但UV反照率的统计学意义不明显，为-0.05 在格陵兰岛内部，每十年10％的强度会发生少量的偶发性下降，这通常在多种仪器中都可以看到。北方森林解释了其中三个变暗事件。其他事件是由表面融化或火山引起的。我们估计校准辐射的2σ不确定度为0.35％。