Proposed MODIS/Aqua reprocessing update

[genecarlfeldman]

Ocean Color/Ocean Biogeochemistry Community:

As we have mentioned in the Ocean Biology Processing Group (OBPG)
progress reports distributed to you over the past few months, we have
been working to better understand and to improve the quality of the
MODIS/Aqua ocean color data set and the consistency between
MODIS/Aqua and SeaWiFS data products, especially the Level-3
products. The initial reprocessing we conducted last spring made a
significant improvement in the comparisons, but we have developed
further algorithm improvements which address some of the remaining
issues such as residual seasonality and longer term trends in the
comparisons. Also, the calibration tables in the operational
processing are deviating significantly from more recent solar and
lunar observations, so a reprocessing needs to be executed regardless
of other improvements. We have completed over 30 time series tests
of various calibration, atmospheric correction, and water-leaving
radiance normalization schemes and are now recommending a number of
processing improvements for a second MODIS/Aqua reprocessing. It
should be noted that a number of the algorithm improvements apply to
SeaWiFS processing as well and, in those cases, the SeaWiFS data for
each of those tests was reprocessed with the algorithm change
implemented. Thus, the testing revealed a number of refinements to
both SeaWiFS and MODIS/Aqua.

Rather than enumerate these recommendations here, we invite you to
review them at the website listed below and ask you to provide your
feedback through the Ocean Color Forum under the newly created
"MODIS/Aqua Reprocessing" section. There is one issue, in
particular, that we feel the user community should consider closely,
the application of the Morel, Antoine, and Gentilli f/Q factor to the
water-leaving radiance normalization. The f/Q correction removes
residual seasonality in the open ocean MODIS/Aqua-SeaWiFS
comparisons, but seems to result in a significant bias to the
water-leaving radiance in the coastal subset.

Reprocessing website:
http://oceancolor.gsfc.nasa.gov (/REPROCESSING/Aqua/R1/)

Ocean Color Forum:
http://oceancolor.gsfc.nasa.gov/

The schedule we would like to follow is to allow 2-3 weeks of
discussion, after which time Paula Bontempi would authorize the
reprocessing using whichever refinements she and the community deem
best, e.g., whether or not to apply the f/Q correction. Once the
green light is given, the OBPG would initiate the reprocessing which
we expect will take about 2 weeks.

We look forward to your comments and suggestions and we hope that the
results posted on the reprocessing website are helpful in your
deliberations.

Chuck McClain, Gene Carl Feldman, and the OBGP staff