Validation of Remote-Sensing Algorithms for Diffuse Attenuation of Downward Irradiance Using BGC-Argo Floats

作     者：Demeaux, Charlotte Begouen Boss, Emmanuel 

作者机构：Univ Maine Sch Marine Sci Orono ME 04469 USA 

出 版 物：《REMOTE SENSING》 (遥感)

年 卷 期：2022年第14卷第18期

页      面：4500-4500页

核心收录：

学科分类：0830[工学-环境科学与工程（可授工学、理学、农学学位）] 1002[医学-临床医学] 070801[理学-固体地球物理学] 07[理学] 08[工学] 0708[理学-地球物理学] 0816[工学-测绘科学与技术] 

基　　金：NASA Ocean Biology and Biogeochemistry program [80NSSC20M0203] 

主　　题：radiometry diffuse attenuation coefficient algorithm validation ocean optics BGC-Argo 

摘      要：Estimates of the diffuse attenuation coefficient (K-d) at two different wavelengths and band-integrated (PAR) were obtained using different published algorithms developed for open ocean waters spanning in type from explicit-empirical, semi-analytical and implicit-empirical and applied to data from spectral radiometers on board six different satellites (MODIS-Aqua, MODIS-Terra, VIIRS-SNPP, VIIRS-JPSS, OLCI-Sentinel 3A and OLCI-Sentinel 3B). The resultant K(d)s were compared to those inferred from measurements of radiometry from sensors on board autonomous profiling floats (BGC-Argo). Advantages of BGC-Argo measurements compared to ship-based ones include: 1. uniform sampling in time throughout the year, 2. large spatial coverage, and 3. lack of shading by platform. Over 5000 quality-controlled matchups between K(d)s derived from float and from satellite sensors were found with values ranging from 0.01 to 0.67 m(-1). Our results show that although all three algorithm types provided similarly ranging values of K-d to those of the floats, for most sensors, a given algorithm produced statistically different K-d distributions from the two others. Algorithm results diverged the most for low K-d (clearest waters). Algorithm biases were traced to the limitations of the datasets the algorithms were developed and trained with, as well as the neglect of sun angle in some algorithms. This study highlights: 1. the importance of using comprehensive field-based datasets (such as BGC-Argo) for algorithm development, 2. the limitation of using radiative-transfer model simulations only for algorithm development, and 3. the potential for improvement if sun angle is taken into account explicitly to improve empirical K-d algorithms. Recent augmentation of profiling floats with hyper-spectral radiometers should be encouraged as they will provide additional constraints to develop algorithms for upcoming missions such as NASA s PACE and SBG and ESA s CHIME, all of which will include a hyper