Ocean-color radiometry across the Southern Atlantic and Southeastern Pacific: Accuracy and remote sensing implications

TitleOcean-color radiometry across the Southern Atlantic and Southeastern Pacific: Accuracy and remote sensing implications
Publication TypeJournal Article
Year of Publication2014
AuthorsRudorff N.D, Frouin R., Kampel M., Goyens C., Meriaux X., Schieber B., Mitchell B.G
JournalRemote Sensing of Environment
Volume149
Pagination13-32
Date Published2014/06
Type of ArticleArticle
ISBN Number0034-4257
Accession NumberWOS:000337651300002
Keywordsabove-water; atlantic; Bio-optics; diffuse-reflectance; inherent optical-properties; light-field; natural-waters; ocean color; phase function; pure water; R/V Melville MV1102 cruise; Radiometry; Southeastern Pacific; southern; turbid waters; Uncertainty analysis; variability; water-leaving radiances
Abstract

Ocean color radiometry (OCR) provides valuable data for biogeochemical oceanography. In situ OCR measurements are used in the development and validation of bio-optical models and vicarious calibration of satellite ocean-color sensors. It is thus crucial to obtain accurate in situ OCR measurements, which is a challenge, especially in regions subjected to adverse environmental conditions and where waters are optically complex. In the present work, the accuracy of in situ OCR is analyzed with data acquired in a wide range of bio-geographic provinces across the Southern Atlantic and Southeastern Pacific during the R/V Melville MV1102 cruise. Varied techniques employed to measure above-water remote sensing reflectance (R-rs) are inter-compared. Measured R is also compared with modeled R-rs in a closure experiment. The impact of R-rs uncertainties on the retrieval of chlorophyll a concentration (Chla) and inherent optical properties (IOPs) is evaluated using operational bio-optical algorithms. The relative percent difference (RPD) between R-rs measured by the various techniques ranged from 12 to 26% for the ocean-color bands (412-555 nm), and 3-12% for the ratios (412-510/555). A merged R-rs obtained by averaging the different types of measurements, INS, is recommended to reduce uncertainties. The coefficient of variation of INS and reflectance ratios was 11-13% and 3-5%, respectively. The RPD between INS and modeled R-rs and the corresponding ratios ranged from 18 to 34% and from 13 to 17%, respectively. Complete closure could not be obtained due to both measurement and modeling uncertainties. The impact of INS uncertainties on retrieved Chla and IOPs was generally smaller than the intrinsic errors of the inversion schemes. The results suggest that even though more accurate ocean-color radiometry is desirable, improving retrieval algorithms is essential to properly describing and furthering our understanding of bio-optical variability in the world's oceans. (C) 2014 Elsevier Inc All rights reserved.

DOI10.1016/j.rse.2014.03.029
Short TitleRemote Sens. Environ.
Integrated Research Themes: 
Student Publication: 
No