Three Announcements

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Three Announcements

by genecarlfeldman » Wed Aug 17, 2005 3:39 pm America/New_York

Good afternoon,
Below are three important updates from the our group involving 1) OCTS and CZCS data set updates as part of the climate data record development 2) SeaDAS update 3) New product feature on the Level-3 browser 4) Migration of MODIS SST processing

1) As part of the NASA Ocean Biogeochemistry Programs strategy to develop and maintain climate data records derived from ocean color satellites, a group of us at Goddard Space Flight Center (Watson Gregg, PI) has been funded under the REASoN-CAN to refine and update the products from certain historical missions, i.e., those not currently operational. Specifically, we have been working on the CZCS and OCTS (4-km data). Our work is aimed at maintaining the CZCS and OCTS data sets at a level that is as consistent as possible with our current SeaWiFS and MODIS data sets, but also recognizing that there may be limitations to the data quality level we can actually achieve due to coverage, our understanding of the sensor performance characteristics, in situ data availability, etc. In order to enable you, the community, to interact with us as we proceed in revising the products we generate from these two missions, we are making the level-1 data available via the Ocean Color website and will be updating SeaDAS to include the our most recent processing code for each. Note that in both cases, we are not ready to distribute Level-2 and Level-3 data although these products can be displayed using the Ocean Color browser. There is much to do in terms of evaluations and refinements in the processing procedures.

Current Status:
CZCS: The work we have completed thus far under the REASoN-CAN includes the recreation of the level-1 data set to remove duplicate data (e.g., duplicate scenes and duplicate pixels from overlapping passes) using a set of data quality selection criteria. We are also working on updating the navigation of the data set and are exploring alternative methods for the time-dependent vicarious calibration. At this time it is possible to browse the level-1 and level-2 data but not to download them until the navigation issues have been resolved.

OCTS: In 2000, the SeaWiFS-SIMBIOS Project Office collaborated with the Japanese space agency (formerly NASDA) in reprocessing the 4-km global OCTS ocean color data. We are revisiting that data set to incorporate the long list of algorithm improvements (atmospheric and bio-optical) that have been implemented in the SeaWiFS and MODIS processing since 2000. We have updated the processing code and are currently reviewing the results of the first global test processing for possible biases in the water-leaving radiances and time trends in the atmospheric correction products. You can download the Level-1 data from the browser. The latest version of SEADAS (4.8) has the ability to process the Level-1 OCTS GAC products to Level-2. By default, the algorithms employed for atmospheric correction are effectively identical to those used for SeaWiFS and MODIS/Aqua (including f/Q corrections, Thuillier solar model, TOMS V8 ozone, etc.). An updated vicarious calibration will be posted on the SeaDAS website, which will allow users to reproduce the products currently visible on the Level-2 Browser. However, a preliminary analysis of this initial processing configuration indicates probable temporal trends in the instrument calibration and unexplained negative bias in the nLw retrievals. Future updates will attempt to address these issues.

2) Dear SeaDAS Users,

SeaDAS 4.8 Update 01 is now available on our ftp site. This update
provides only the new MODIS Aqua LUT's and gains used in the recent
Aqua Reprocessing 1.1. Applying this update will ensure that your
Aqua processing matches our production data. There is an INSTRUCTIONS
file located in the update01 directory on our ftp site that will tell
you how to apply this update. It is also here for your convenience:

Instructions for installing SeaDAS 4.8 Update 01

This update provides the newest MODIS Aqua calibration LUT's and
gain values, corresponding to those values used in the latest Aqua
Reprocessing 1.1. Note that you must run seadas_setup after
installing this update, prior to running seadas, so that the LUT
environment variables will be set correctly.

NOTE: If you have not installed SeaDAS 4.8 yet, you do need to
install this update after installing the main software, since this
update is not included in the main tar file distributions.

1. Create a directory on your computer to hold the update 01 files:
mkdir update01
2. cd to that directory:
cd update01
3. Anonymously ftp to
4. After logged in, switch to binary mode:
5. Change directory to where the update files are located:
cd seadas/seadas/update01
6. Get the zipped tar file for the update:
get update01.tar.gz
7. Log off of ftp
8. Unzip and extract the update files:
gunzip -c update01.tar.gz | tar xvf -
9. Make sure that your $SEADAS environment variable is set correctly:
setenv SEADAS /wherever/your/seadas4.8/is/located (for c shell)
or export SEADAS=/wherever/your/seadas4.8/is/located (for bash shell)
10. Run the update_01.csh script to install the files:
11. Run the seadas_setup script:
cd ..
12. Enjoy and let us know if you have any problems.

The SeaDAS Development Group (

3) A new three-day rolling average quick-look global chlorophyll product for MODIS/AQUA is now available at both 4 and 9 kilometer on the Level-3 browser at:

This image and HDF file is produced each day using the quick-look data for the previous three days and balances increased coverage with preserving the short-term variability in the data. The data are also available via ftp under the link "Mapped Daily / 3Day Quicklook" directory found on:

Best regards from the Ocean Biology Processing Group


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