SeaWiFS Level-3 chlorophyll anomaly products

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SeaWiFS Level-3 chlorophyll anomaly products

by genecarlfeldman » Wed Jun 14, 2006 12:15 pm America/New_York

We have just added a new product to the Level-3 web browser that might be of interest to people. Based on the nearly nine year SeaWiFS data record, we have started to produce a chlorophyll-a anomaly product derived for each year, season, and month of the SeaWiFS mission. These products are produced by subtracting the climatological averages for each time period from the averages for just the period
under consideration starting with September 1997 and continuing through the most recently produced monthly average. The differences in milligrams per cubic meter are then logarithmically scaled such that increases of 0.01 to 10 milligrams per cubic meter with respect to the climatology get assigned colors on the positive-anomaly portion of the image color scale while decreases of the same amounts get assigned colors along the negative-anomaly portion of the color scale. In addition to presenting the anomaly image (png-formatted images are all that are available at this time. hdf files will be available in the future), access to the climatological image or corresponding single period image is also available for comparison. More details about how these products are currently being produced and even the little Perl script that is used to compute them are available on the webpage. The anomaly products can be reached directly at:

or via the link at the top of the Level-3 Browse page. A good example of how one can use these anomaly maps is to look at the impact of the 1997/1998 El Nino/La Nina on the chlorophyll-a concentrations in the Equatorial Pacific. Looking at the El Nino conditions represented in the Autumn 1997 anomaly image, one can quite clearly see the depressed chlorophyll-a concentrations across the entire equatorial region and the even greater impact along the coasts of Ecuador and Peru.

Autumn 1997: ... CHLO_9.png

In contrast, the Summer 1998 anomaly image shows the remarkably elevated chlorophyll-a concentrations along the equator and the region between the Galapagos and the coast of South America resulting from the dramatic transition to La Nina conditions.

Summer 1998: ... CHLO_9.png

A far more comprehensive image analysis, display and plotting tool for these data sets plus many others can be found at the GES-DISC Interactive Online Visualization and ANalysis Infrastructure (Giovanni) webpage:

Have fun and as always, comments and suggestions are always appreciated.


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