A likely candidate is rising ultraviolet radiation as a result of either ozone depletion, or a change in the level of cloud cover.
一个可能的原因是臭氧耗竭或云层高度改变引起紫外线辐射增强。
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The OMI sensor can distinguish the differences between cloud, smoke, dust, ozone and other aerosols, and is important in Earth observations for aviation safety. AP / NOAA