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首页> 外文期刊>Journal of oceanography >Evaluation of ADEOS-II GLI ocean color atmospheric correction using SIMBADA handheld radiometer data
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Evaluation of ADEOS-II GLI ocean color atmospheric correction using SIMBADA handheld radiometer data

机译：使用SIMBADA手持辐射计数据评估ADEOS-II GLI海洋色彩大气校正

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The performance of the “version 2” Global Imager (GLI) standard atmospheric correction algorithm, which includes empirical absorptive aerosol correction and sun glint correction, was evaluated using data collected with handheld above-water SIMBADA radiometers during 23 cruises of opportunity (research vessels, merchant ships), mostly in the North Atlantic and European seas. A number of 100 match-up data sets of GLI-derived and SIMBADA-measured normalized water-leaving radiance (nLW) and aerosol optical thickness (AOT) were sorted out, using objective selection criteria, and analyzed. The Root-Mean-Square (RMS) difference between GLI and SIMBADA nLW was about 0.32 μW/cm2m/sr for the 412 nm band, showing improvement by 30% in RMS difference with respect to the conventional “version 1” GLI atmospheric correction algorithm, and the mean difference (or bias) was reduced significantly. For AOT, the RMS difference was 0.1 between GLI estimates and SIMBADA measurements and the bias was small (a few 0.01), but the ?ngstr?m exponent was systematically underestimated, by 0.4 on average, suggesting a potential GLI calibration offset in the near infrared. The nLW differences were not correlated to AOT, although performance was best in very clear conditions (AOT less than 0.05 in the 865 nm band). Despite the relatively large scatter between estimated and measured nLW, the derived chlorophyll-a concentration estimates, applying the same ratio algorithm (GLI OC4V4) to GLI and SIMBADA, were consistent and highly correlated in the range of 0.05–2 μg/l. The large variability in chlorophyll-a concentration estimate for clear clean water areas (e.g. with the concentration range lower than about 0.05 μg/l) turns out to be due to the nature of the “band ratio” based in-water algorithm.
机译：在23次机会巡游中（使用研究型船只，研究型船只），使用手持式水上SIMBADA辐射计收集的数据对“版本2” Global Imager（GLI）标准大气校正算法（包括经验性吸收气溶胶校正和太阳闪烁校正）的性能进行了评估。商船），大部分在北大西洋和欧洲海域。使用客观选择标准，对GLI衍生和SIMBADA测量的归一化放水辐射率（nLW）和气溶胶光学厚度（AOT）的100个匹配数据集进行了分类，并进行了分析。对于412 nm波段，GLI和SIMBADA nLW之间的均方根（RMS）差约为0.32μW/ cm2 / nm / sr，与传统的“版本1” GLI大气相比，RMS差提高了30％校正算法，平均差（或偏差）显着减小。对于AOT，GLI估计值与SIMBADA测量值之间的RMS差为0.1，偏差很小（约0.01），但系统误差被系统低估了，平均降低了0.4，表明在附近存在潜在的GLI校准偏差红外线。尽管在非常清晰的条件下性能最佳（865nm波段的AOT小于0.05），nLW的差异与AOT无关。尽管估计的nLW和测量的nLW之间存在较大的差异，但对GLI和SIMBADA应用相同的比率算法（GLI OC4V4）得出的叶绿素a浓度估计值在0.05–2μg/ l的范围内是一致且高度相关的。明确的清洁水域（例如，浓度范围低于约0.05μg/ l）的叶绿素a浓度估算值存在很大差异，这是由于基于“谱带比”的水中算法的性质所致。

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