First steps in the creation of a Joint MISR/MODIS Ocean Color Atmospheric Correction algorithm

We are creating a new algorithm that combines observations from MISR and MODIS (both on the NASA Terra spacecraft) to improve atmospheric correction and coverage for ocean color data products. The algorithm utilizes information rich, multi-angle MISR observations for atmospheric correction, applied to MODIS. Our goal is to produce atmospherically corrected Remote Sensing Reflectance from MODIS with enhanced coverage and accuracy, for input to downstream bio-optical ocean parameter retrieval algorithms.

An important aspect of this work is the utilization of multi-angle views of the reflected ocean surface sun glint. Usually, such observations are avoided, since the intensity of the glint overwhelms any contribution from the ocean body. However, MISR's multi-angle observations see varying degrees of glint, which means they can be used to better determine aerosol optical properties (Kaufman et al., 2002, Ottaviani et al., 2013), and to identify surface wind speeds that govern the glint pattern. The latter could be utilized to replace the wind speeds taken from ancillary sources that are currently used to conservatively mask potential glint contamination in MODIS observations.

To assess this capability, and to identify the appropriate parameterization, we present an analysis using the Generalized Nonlinear Retrieval Analysis (GENRA, Vukicevic et al., 2009) information content assessment. This technique is also easily modified to act as a Bayesian retrieval algorithm, for which initial results are discussed. Finally, we describe the status of integrating MISR data into the processing capabilities of the Ocean Biology Processing Group (OBPG) at NASA, and show the first ocean color vicarious calibration (Franz et al., 2007) of the MISR instrument.

Franz, B. A., et al., 2007. Sensor-independent approach to the vicarious calibration of satellite ocean color radiometry. Appl Opt, 46 (22): 5068-5082.

Kaufman, Y. J., et al., 2002. Satellite retrieval of aerosol absorption over the oceans using sunglint, Geophys. Res. Lett., 29, 34-1.

Ottaviani, M., et al., 2013. Information content of aerosol retrievals in the sunglint region. Geophys. Res. Lett., 40(3), 631-634.

Vukicevic, T., et al., 2010. Characterizing the retrieval of cloud properties from optical remote sensing. J. of Geophys. Res.: Atmospheres, 115(D20).