Sensitivity of Satellite Ocean Color Data to System Vicarious Calibration of the Long Near Infrared Band
Sensitivity of Satellite Ocean Color Data to System Vicarious Calibration of the Long Near Infrared Band
复制标题
DOI：
10.1109/tgrs.2020.3000475
复制
发表时间：
2021-03
影响因子：
8.2
通讯作者：
B. Barnes;Chuanmin Hu;S. Bailey;B. Franz
中科院分区：
文献类型：
--
作者：
B. Barnes;Chuanmin Hu;S. Bailey;B. Franz
卫星海洋水色任务需要精确的系统替代定标（SVC）来从at-sensor辐射率中恢复相对较小的遥感反射率（$R_{\mathrm {rs}}$，sr-1）。然而，目前的大气校正和SVC程序不包括校准的“长”近红外波段（NIRL-869 nm的中分辨率成像光谱仪），部分原因是早期的研究，主要是基于模拟，表明在检索$R_{\mathrm {rs}}$的准确性是不敏感的温和变化的NIRL替代增益（$g$）。然而，海洋颜色数据产品的敏感性$g$（NIRL）尚未得到彻底的检查。在这里，我们首先得出10 SVC的“增益配置”（所有可见光和近红外波段的替代增益）的MODIS/水使用当前的操作NASA协议，每次假设不同的$g$（869）。从这些，我们得到一套~1.4E6独特的增益配置与$g$（869）范围从0.85到1.2。所有的MODIS/A数据的25个位置内的每个五个海洋环流，然后使用这些增益配置进行处理。结果时间序列显示，响应于$g$（869）（以及相关增益配置）的变化，主导$R_{\mathrm {rs}}$（547）模式存在显着变化。总的来说，平均R_{rs}$（547）值通常随着g$（869）的增加而减少，而这些平均值周围的标准差显示，使用这样的时间序列，g $（869）= 1.025与预期最接近。这种方法是广泛适用于其他海洋颜色传感器，并强调了严格的跨传感器校准的NIRL波段的重要性，合并传感器数据集的一致性的影响。
Satellite ocean color missions require accurate system vicarious calibrations (SVC) to retrieve the relatively small remote-sensing reflectance ( $R_{\mathrm {rs}}$ , sr−1) from the at-sensor radiance. However, the current atmospheric correction and SVC procedures do not include calibration of the “long” near infrared band (NIRL—869 nm for MODIS), partially because earlier studies, based primarily on simulations, indicate that accuracy in the retrieved $R_{\mathrm {rs}}$ is insensitive to moderate changes in the NIRL vicarious gain ( $g$ ). However, the sensitivity of ocean color data products to $g$ (NIRL) has not been thoroughly examined. Here, we first derive 10 SVC “gain configurations” (vicarious gains for all visible and NIR bands) for MODIS/Aqua using current operational NASA protocols, each time assuming a different $g$ (869). From these, we derive a suite of ~1.4E6 unique gain configurations with $g$ (869) ranging from 0.85 to 1.2. All MODIS/A data for 25 locations within each of five ocean gyres were then processed using each of these gain configurations. Resultant time series show substantial variability in dominant $R_{\mathrm {rs}}$ (547) patterns in response to changes in $g$ (869) (and associated gain configurations). Overall, mean $R_{\mathrm {rs}}$ (547) values generally decrease with increasing $g$ (869), while the standard deviations around those means show gyre-specific minima for $0.97 (869) $g$ (869) using such time series, finding $g$ (869) = 1.025 most closely comports with expectations. This approach is broadly applicable to other ocean color sensors, and highlights the importance of rigorous cross-sensor calibration of the NIRL bands, with implications on consistency of merged-sensor data sets.