Atmospheric Correction for the NPP VIIRS Ocean Color EDRs

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 Atmospheric Correction for the NPP VIIRS Ocean
Color EDRs 

• Menghua Wang
• University of Maryland Baltimore County
• NASA Goddard Space Flight Center, Code
  970.2Greenbelt, MD 20771, USA
• NPP Science Team Meeting
• November 4-6, 2003, Annapolis, Maryland  

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Atmospheric Correction
Atmospheric Correction Algorithm (Gordon Wang,
1994)

• rw is the desired quantity in ocean color
  remote sensing the VIIRS ocean color EDRs.
• Trg is the sun glint contribution
  avoided/masked and residual contamination is
  corrected.
• trwc is the whitecap reflectance computed from
  wind speed.
• rr is the scattering from molecules computed
  using the Rayleigh lookup tables.
• ?A ra rra is the aerosol and Rayleigh-aerosol
  contributions estimated using aerosol models.

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Examples of the TOA Reflectance
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Validation Results from SeaWiFS
http//seawifs.gsfc.nasa.gov/SEAWIFS
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Chlorophyll Results from SeaWiFS
http//seawifs.gsfc.nasa.gov/SEAWIFS
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EDR/CDR List

• The spectrum of water-leaving radiances (the
  ocean color EDRs).
• The necessary vicarious calibration technique for
  the ocean color EDRs.
• The band ratio values of the water-leaving
  radiance spectrum that are used for deriving the
  chlorophyll concentration and other ocean
  bio-optical EDRs.
• Possibly look into the chlorophyll and ocean
  optical property EDRs.
• Aerosol optical property data over ocean, which
  are derived as by-products from the atmospheric
  correction (results may be useful for evaluation
  of the aerosol EDRs).

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Roles of PI and Co-I

• Menghua Wang will assume the overall
  responsibility for the project, and may get an
  assistant for helps in data analyses.
• radiative transfer modeling, ocean color remote
  sensing, remote retrievals and in situ
  measurements of aerosol optical and microphysical
  properties, calibration and validation
  techniques, and data merging methods for various
  satellite remote sensors.
• Interested in and welcome collaborations from NPP
  PIs and Co-Is, and Northrop Grumman Space
  Technologies (NGST).

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Approach

• Assessment of spatial and temporal uncertainties
  of the ocean color EDRs that are processed using
  the VIIRS atmospheric correction algorithm.
  These include evaluation of the algorithm for
• the instrument polarization sensitivity
• algorithm performance in the coastal regions
  (e.g., absorbing aerosols, Case-II waters)
• effects of ancillary data variability
• solar-sensor geometry (e.g., high latitude
  regions, Earth curvature effects)
• and some other effects, e.g., aerosol models
• Evaluation of the vicarious calibration with
  various spatial and temporal uncertainties and
  some other effects.

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Resources Offered/Requested

• Studies will be carried out using both the
  simulated and satellite data, e.g., measurements
  from MODIS and SeaWiFS. Experiences and lessons
  learned from the MODIS and SeaWiFS ocean color
  missions are extremely useful for the NPP
  project.
• In situ data from the SeaBAS (SeaWiFS Bio-Optical
  Archive and Storage System) and from other data
  sources are planned for use.
• The data analyses for SeaWiFS and MODIS can be
  achieved using the SeaDAS (SeaWiFS Data Analysis
  System) software, which is freely available and
  widely distributed.
• Assume computer resources and necessary supplies
  are provided through NASA/GSFC.

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Contribution to Deliverables

• It is expected that all analysis results,
  algorithm sensitivity studies, and proposed
  algorithm improvements will be published in
  peer-reviewed journals and/or in technical
  reports.
• Studies using the MODIS and SeaWiFS data are
  particularly important and useful.