The difference 8 days makes: new ocean color radiometry data increase information in space and time

               The NASA Giovanni data system, hosted at the Goddard Earth Sciences Data and Information Services Center (GES DISC), provides a wide variety of mapped earth science data parameters from NASA missions and projects for the scientific community.   Many of these data parameters are provided as data averaged over monthly periods (though Giovanni does have some data sets with daily, 3-hour, and even hourly temporal resolution).    For the past few years, the only ocean color radiometry data sets in Giovanni have been monthly averages – and these data sets do not always capture the remarkably varying patterns  in the global oceans.

                Now, as part of the Water Quality for Coastal and Inland Waters Project (Zhongping Lee, University of Massachusetts – Boston, PI;   James Acker, GES DISC/Wyle IS LLC, Co-I, and others), ocean color radiometry data at 8-day resolution is now available in Giovanni.   These data are available at 4 km and 9 km spatial resolution for the Moderate Resolution Imaging Spectroradiometer (MODIS), and at 9km resolution for the Sea-viewing Wide Field-of-view Sensor (SeaWiFS).   Together, these data comprise a 13-year observational period, beginning in September 1997 for SeaWiFS.

                In addition to the standard NASA data products, Giovanni is providing, for the first time, evaluation data products which include absorption coefficients and backscattering coefficients, also at 8-day resolution. Such data can yield remarkable insight into the timing of ocean optical events related to storms and floods and their effect on the coastal zone, as well as a better characterization of the growth and senescence phases of phytoplankton blooms.

                The figures below show a dynamic area of the ocean, the Pacific coast of Central America (subject of the Science Focus! article “The Papagayo Wind”). The winter wind jets that mix the surface ocean and cause episodic phytoplankton blooms create rapidly changing patterns of ocean color in this region.   The first image is the monthly average for January 2005 – the four subsequent images are the corresponding 8-day images for this month. As can be seen, while the monthly image shows the general pattern of phytoplankton activity corresponding to the wind jet-affected zones, the 8-day images show how the wind-induced blooms move and interact during the period.  

Figure 1.  Giovanni image of monthly average MODIS chlorophyll a concentration for January 2005, centered on the winter wind jet region of the Pacific Ocean coast of Central America.  Click on this image to view it larger.

Figure 2.  Giovanni animation of four 8-day MODIS chlorophyll a concentration images for January 2005, centered on the winter wind jet region of the Pacific Ocean coast of Central America.

Figure 3.  Individual 8-day Giovanni images of MODIS 8-day chlorophyll a concentrations for January 2005, centered on the winter wind jet region of the Pacific Ocean coast of Central America.  Clicking on any of these images will provide a larger view.

Acknowledgments:

MODIS and SeaWiFS data products are produced by the Ocean Biology Processing Group, http://oceancolor.gsfc.nasa.gov.

Funding for support of ocean color radiometry data in Giovanni is provided through the "Water Quality for Coastal and Inland Waters Project", NNX09AV57G, from the National Aeronautics and Space Administration (NASA), and the National Oceanographic Partnership Program (NOPP) project, "Development, Assessment and Commercialization of a Biochemical Profiling Float for Calibration and Validation of Ocean Color and Ocean Carbon Studies" (Emmanuel Boss, University of Maine, PI).

The GES DISC and the Ocean Biology Processing Group are NASA earth science data centers, part of the NASA Earth Science Data and Information System (ESDIS) Project.