Abstract. Non-linear effects, such as from saturation, stray light, or obstruction of light, negatively impact satellite measured ultraviolet and visible Earthshine radiance spectra and downstream retrievals of atmospheric and surface properties derived from these spectra. In addition, excessive noise such as from cosmic ray impacts, prevalent within the South Atlantic Anomaly, can also degrade satellite radiance measurements. Saturation specifically pertains to observations of very bright surfaces such as sun glint over water surfaces or thick clouds. Related residual electronic cross-talk or blooming effects may occur in spatial pixels adjacent to a saturated area. Obstruction of light can occur within the zones of solar eclipses as well as from material located outside of the satellite instrument. The latter may also produce unintended scattered light into a satellite instrument. When these effects cannot be corrected to an acceptable level for science quality retrievals, it is desirable to flag the affected pixels. Here, we introduce a new detection method that is based on the correlation, r, between the observed Earthshine radiance and solar irradiance spectra over a 10 nm-spectral range; our Decorrelation Index (DI for brevity) is simply defined as DI=1−r. DI increases with non-linear effects or excessive noise in either radiances (the most likely cause in OMI data) or irradiances. DI is relatively straight-forward to use and interpret and can be computed for different wavelength intervals. We developed a set of DIs for two spectral channels of the Ozone Monitoring Instrument (OMI), a hyperspectral pushbroom imaging spectrometer. For each OMI spatial measurement, we define 14 wavelength-dependent DIs within the OMI visible channel (350–498 nm) and 6 DIs in its ultraviolet 2 (UV2) channel (310–370 nm). As defined, DIs reflect a continuous range of deviations of observed spectra from the reference irradiance spectrum that are complementary to the binary Saturation Possibility Warning (SPW) flags currently provided for each individual spectral/spatial pixels in the OMI radiance data set. Smaller values of DI are also caused by a number of geophysical factors; this allows one to obtain interesting physical results on the global distribution of spectral variations.

中文翻译：

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卫星紫外线/可见光反射光谱中非线性效应的检测：在臭氧监测仪中的应用

摘要。非线性影响，例如来自饱和，杂散光或光的阻挡，会对卫星测量的紫外线和可见的大地辐射光谱产生负面影响，并从这些光谱得出的下游大气和表面特性的反演结果。此外，在南大西洋异常内部普遍存在的过多噪声（例如，宇宙射线撞击产生的噪声）也会使卫星辐射测量值降低。饱和度特别适用于观察非常明亮的表面，例如在水表面或厚厚的云层上出现日照。在邻近饱和区域的空间像素中可能会发生相关的残余电子串扰或泛光效应。在日食区域内以及来自卫星仪器外部的材料都可能发生光障。后者也可能向卫星仪器中产生意外的散射光。如果无法将这些影响校正到科学质量检索可接受的水平，则需要标记受影响的像素。在这里，我们介绍一种基于相关性的新检测方法，r，在10 nm光谱范围内观察到的大地辐射和太阳辐射光谱之间；我们的解相关指数（为简洁起见，DI）简单定义为DI = 1− r。DI随非线性效应或辐射（OMI数据中最可能的原因）或辐射中的过多噪声而增加。DI使用和解释相对简单，可以针对不同的波长间隔进行计算。我们为臭氧监测仪（OMI）（一种高光谱推扫式成像光谱仪）的两个光谱通道开发了一套DI。对于每个OMI空间测量，我们在OMI可见通道（350–498 nm）内定义14个与波长相关的DI，在其紫外线2（UV2）通道（310–370 nm）中定义6个DI。根据定义，DI反映了观察光谱与参考辐照光谱的连续偏差范围，该偏差与当前为OMI辐射数据集中的每个单独光谱/空间像素提供的二进制饱和可能性警告（SPW）标志互补。DI的较小值也是由许多地球物理因素引起的。这使人们可以获得有关光谱变化全局分布的有趣的物理结果。