Correction for the non-nadir viewing geometry of AERONET-OC above water radiometry data: an assessment of uncertainties.

• Published in: Optics Express
• Main Authors: TALONE Marco, ZIBORDI Giuseppe, LEE Zhongping
• Language: English
• Published: OPTICAL SOC AMER 2018
• Subjects: Aerosol Robotic Network
• Online Access: https://publications.jrc.ec.europa.eu/repository/handle/JRC109142; https://www.osapublishing.org/oe/abstract.cfm?uri=oe-26-10-A541; https://doi.org/10.1364/OE.26.00A541

The effects of non-nadir viewing geometry in above-water radiometry data were investigated using field measurements and two different correction approaches: one centered on chlorophyll-a concentration (Chla) applicable to Case-1 waters, and the other relying on seawater inherent optical properties (IOP) proposed for any water type. With specific reference to data from the Ocean Color component of the AErosol RObotic NETwork (AERONET-OC), the study focused on the assessment of the uncertainties affecting corrections for non-nadir view of data collected with 40° in-air viewing angle and 90° relative azimuth between viewing direction and sun. The study analyzed AERONET-OC water-leaving radiance data from different European seas to determine differences between corrections performed with the Chla- and the IOP-based approaches. Additionally, data collected in waters characterized by different optical complexity and comprising water-leaving radiances measured at nadir and with 28.6° in-water viewing angle (corresponding to 40° in-air), both with 90° relative azimuth, were used to investigate the uncertainties of the two correction approaches. For data from AERONET-OC sites characterized by a variety of optically complex waters, results indicated corrections with uncertainties between 20 and 30% from 412 to 670 nm for the IOP-based approach and conversely largely varying with wavelength and water type for the Chla-based one with values of approximately 55% at 412 nm, 20-40% between 490 and 560 nm, and exceeding 60% at 670 nm. JRC.D.2 - Water and Marine Resources