MODIS-Aqua ocean color climatologies allow 10 years of anomaly analysis
New insights possible from higher spatial resolution and new data products
The incorporation of the recently released 10-year climatology of ocean color data from NASA's Moderate Resolution Imaging Spectroradiometer on the Aqua satellite (MODIS-Aqua) allowed the Giovanni data system to provide anomaly analysis for this important ocean data set.
The Earth Observing System Aqua satellite was launched in early 2002, and the onboard MODIS instrument began collecting data on July 4, 2002. Thus, at the end of June 2012, there were 10 years of monthly averaged MODIS data for each month of the year. The Ocean Biology Processing Group (OBPG) at Goddard Space Flight Center updates their monthly climatology files as each new month is completed. In July 2012, the NASA Goddard Earth Sciences Data and Information Services Center (GES DISC) acquired these monthly climatology files to create a 10-year climatology base period for the Giovanni data system.
With the climatology files in Giovanni, researchers could then examine these climatological averages, or use the new data for anomaly analysis. The latter enhances the detection of unusual events in any long-term data set, by comparing data from a selected period to the average of the data for a much longer period (i.e., "base period"). For ocean color data in Giovanni, anomaly analysis has been available for the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) for several years, but the SeaWiFS mission ended in December 2010. For MODIS-Aqua ocean color climatology data, the mission is still continuing. Furthermore, MODIS-Aqua data are available at 4 km spatial resolution, rather than the 9 km spatial resolution of SeaWiFS data.
Several new data products are available from MODIS-Aqua, including normalized fluorescence line height (nFLH), colored dissolved organic matter (CDOM) Index, absorption coefficients for dissolved and detrital matter (acdm) and phytoplankton (aph), backscattering coefficient for particulate matter (bbp), and euphotic depth (Zeu). The MODIS-Aqua climatology data also provide remote-sensing reflectance data at several more wavelengths than were available from SeaWiFS.
Giovanni's anomaly analysis capability allows users to examine monthly anomalies, and any other time period up to a year in duration. So, for example, it is possible to average data for a season (such as the spring months of March, April, and May of a particular year) and compare this three-month average to the climatological average for March through May.
Full article, with example images: < http://1.usa.gov/WQB7mZ >