The main aim of the MODIS ocean processing code is to calculate level 2, 3, and 4 ocean products from level 1B satellite radiance data. This process is performed in several stages, where the ocean color and sea-surface temperature (SST) level 2 products are first calculated, followed by space and time-binning to retrieve level 3 products, and statistical mapping to yield level 4 products.
The code is divided into six main components: ocean color processing (MODCOL), sea-surface temperature processing (MODSST), space-binning (MSBIN), time-binning (MTBIN), 24-day reference calculating (MFILL) and cloud flagging (MCLOUD); and two subsidiary components: a routine to change the spatial resolution of the binned data (MSPC) and a mapping routine (MMAP). Each of these components can be run separately, and are described in this document.
The ocean color processing routine (MODCOL) includes atmospheric correction algorithms to convert level 1B radiances to water-leaving radiances, as well as algorithms to derive level 2 ocean color products such as chlorophyll concentration. The principles behind each of the algorithms used are discussed in the relevant Algorithm Theoretical Basis Documents (ATBDs). A brief summary of each algorithm can be found in the accompanying document : MODIS Ocean ATBD Summaries. A more general description of the ocean color algorithms can be found at the MODIS Ocean Discipline Group web page.
The sea-surface temperature processing routine (MODSST) is similar in structure to MODCOL. Details of the algorithms used can be found in ATBD25.
The space-binning programs (MSBIN) bin each of the ocean color and SST products into equal-area space bins. Details of the binning method can be found in ATBD26.
The time-binning programs (MTBIN) time bin the space-binned data by orbit, data-day, 8 days, 24 days or monthly. Details of the definition of a data-day can be found in ATBD26.
The routine MFILL calculates 24-day reference values on a global scale by filling in gaps from 24-day time-binned files (output from MTBIN). The reference values are estimated by calculating smoothed, distance-weighted averages of data from surrounding pixels. These reference values are used in MCLOUD.
Cloudy data are flagged using the MCLOUD routine. This routine compares daily data with the 24-day reference from MFILL to determine the sky conditions.
The routine MSPC is used to change the spatial resolution of level 3 files.
The mapping programs (MMAP) map level 3, equal-area, binned data into their geographic projection, producing level 4 data.
Each of these routines are described in more detail in the section Main Program Components.
The standard ocean products derived from this code, along with their product numbers and associated ATBDs, are listed in Table 1 : MODIS Standard Ocean Products. The ocean parameters within these products are listed in Table 11 : MODIS Ocean Parameters.
These routines were coded by : the MODIS Science Data Support Team (SDST); Bob Evans group at RSMAS (University of Miami) - Jim Brown, Sue Walsh, Warner Baringer and Kay Kilpatrick; and by the individual MODIS Ocean Science Team members - Howard Gordon, Otis Brown, Kendall Carder, Steve Ackerman, Dennis Clark, Frank Hoge, Wayne Esaias, Mark Abbott and coworkers. Contact information can be found in the Contacts section.
This set of documents describes each of the components of the MODIS ocean processing routines in detail. The program structures are described, relevant subroutines are documented, and the process of implementation is given.
Documented by Jasmine S. Bartlett, COAS, Oregon State University.