The value and spectral dependence of the reflectance coefficient (ρ) of skylight from wind-roughened ocean surfaces is critical for determining accurate water leaving radiance and remote sensing reflectances from shipborne, AERONET-Ocean Color and satellite observations. Using a vector radiative transfer code, spectra of the reflectance coefficient and corresponding radiances near the ocean surface and at the top of the atmosphere (TOA) are simulated for a broad range of parameters including flat and windy ocean surfaces with wind speeds up to 15 m/s, aerosol optical thicknesses of 0-1 at 440nm, wavelengths of 400-900 nm, and variable Sun and viewing zenith angles. Results revealed a profound impact of the aerosol load and type on the spectral values of ρ. Such impacts, not included yet in standard processing, may produce significant inaccuracies in the reflectance spectra retrieved from above-water radiometry and satellite observations. Implications for satellite cal/val activities as well as potential changes in measurement and data processing schemes are discussed.

Uncertainties in the retrieval of the remote sensing reflectance, Rrs, from Ocean Color (OC) satellite sensors have a strong impact on the performance of algorithms for the estimation of chlorophyll-a, mineral concentrations, and inherent optical properties (IOPs). The uncertainties are highest in the blue bands. The total radiance measured at the top of the atmosphere captures the instantaneous state of the atmosphere-ocean system: the in-water conditions, sky and Sun glint reflected from the wind-roughened ocean surface, as well as light scattered from molecules and aerosols in the atmosphere. Each of these components has associated uncertainties, and when combined with the additional uncertainties from the instrument noise and the atmospheric correction process, they contribute to the total uncertainty budget for the retrieved Rrs. We analyzed the contribution of each component uncertainties to the total Rrs uncertainties in SNPP-VIIRS level 2 products, taking advantage of the spectral differences between the components. We examined multiple scenes in the open ocean and coastal waters at spatial resolutions ranging from 2250 to 5250 m by comparing the retrieved Rrs to in situ measurements made at several AERONET-OC sites and at the MOBY site. It was shown that uncertainties associated with the molecular (Rayleigh) scattering play the most significant role, while the contributions of other components are usually smaller. Uncertainties in Rayleigh scattering are primarily attributed to the variability of Rayleigh optical thickness (ROT) with a standard deviation of approximately 1.5% of ROT, which can largely explain the frequency of negative Rrs retrievals as observed using the current standard atmospheric correction process employed by NASA. Variability of the sky light reflected from the ocean surface in some conditions also contributed to uncertainties in the blue; water variability proportional to Rrs had a very pronounced peak in the green at coastal sites.

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24Comprehensive polarimetric closure is demonstrated using observations from two in-situ 25 polarimeters and Vector Radiative Transfer (VRT) modeling. During the Ship-Aircraft Bio-26Optical Research (SABOR) campaign, the novel CCNY HyperSAS-POL polarimeter was 27 mounted on the bow of the R/V Endeavor and acquired hyperspectral measurements from 28 just above the surface of the ocean, while the NASA GISS Research Scanning Polarimeter was 29 deployed onboard the NASA LaRC's King Air UC-12B aircraft. State-of-the-art, ancillary 30 measurements were used to characterize the atmospheric and marine contributions in the 31 https://ntrs.nasa.gov/search.jsp?R=20180008651 2020-07-07T19:11:16+00:00Z VRT model, including those of the High Spectral Resolution Lidar (HSRL), the AErosol 32 RObotic NETwork for Ocean Color (AERONET-OC), a profiling WETLabs ac-9 spectrometer 33 and the Multi-spectral Volume Scattering Meter (MVSM). An open-ocean and a coastal scene 34 are analyzed, both affected by complex aerosol conditions. In each of the two cases, it is 35 found that the model is able to accurately reproduce the Stokes components measured 36 simultaneously by each polarimeter at different geometries and viewing altitudes. These 37 results are mostly encouraging, considering the different deployment strategies of RSP and 38HyperSAS-POL, which imply very different sensitivities to the atmospheric and ocean 39contributions, and open new opportunities in above-water polarimetric measurements. 40 Furthermore, the signal originating from each scene was propagated to the top of the 41 atmosphere to explore the sensitivity of polarimetric spaceborne observations to changes in 42 the water type. As expected, adding polarization as a measurement capability benefits the 43 detection of such changes, reinforcing the merits of the full-Stokes treatment in modeling 44 the impact of atmospheric and oceanic constituents on remote sensing observations. 45 46