MODCOL | MODSST | MSBIN | MTBIN | MFILL | MCLOUD | MSPC | MMAP
The general flow of these routines is illustrated in Fig. 1 : Code Flowchart.
This program processes level 1B data, creating level 2 ocean color data products. The program first applies atmospheric correction to the level 1B data, and then estimates a suite of ocean color products using a number of ocean color algorithms. Processing occurs for every 5 minutes of satellite data made during the day (144 runs/day). Details of the required inputs, structure and output are given below.
| NOTE : Because of budget constraints, the amount of MODIS realtime processing that can occur within the first 6 months may be limited. To meet these constraints, the amount of processing MAY initially be limited to every 2nd pixel. If needed, this compromise will be reflected in the code. |
The input files required for processing of ocean color data are:
The first four files are obtained from the satellite data itself. The ancillary data are obtained from external files; these are described in more detail below.
All of the relevant coefficients for each of the algorithms are stored in individual ASCII files. The accompanying documentation (Input File Format Description - MODCOL) describes the format and contents of these files. The use of these files was necessary since the requirements for the MODIS code were that the code itself cannot be changed after launch, hence any changes that need to be made must be made through these input files. The names and paths of all of the relevant files are stored in the Process Control File (PCF) for the code (PGE09.pcf).
Meteorological ancillary data is taken from the National Centers for Environmental Prediction (NCEP) (formerly known as the National Meteorological Center (NMC)) and ozone data is taken from TIROS Operational Vertical Sounder (TOVS) measurements. The rules devised for the selection of appropriate climatological ancillary data for a given set of satellite data were as follows:
The relevant PCF for this routine is PGE09.pcf. This file contains an indexed list of filenames and paths of all of the input and output data files to be used by MODCOL. Note that this list also contains items not used in MODCOL (they are used in other components of MODIS processing). The items beginning with index numbers in the range 300,000-399,999 are relevant only to MODCOL, however MODCOL does use some of the other items (which are from other sources) as input.
The relevant MCFs for the MODCOL routine are: MODOCL2.mcf, MODOCL2A.mcf, MODOCL2B.mcf and MODOCQC.mcf.
This file contains the main subroutine ANLSUB that calls all of the other MODCOL processing routines. An ordered list of the main called routines can be found in Table 9 : MODCOL Components.
After initialization, ANLSUB first calls the atmospheric correction routine (newatm) and then all of the ocean color product routines in turn (coccolith, hoge_run, carder_interp, carder_ipar and carder_cweps). Note that the Clark and Abbott algorithms are embedded within ANLSUB - they are not separate subroutines. Brief descriptions of each of these subroutines are given in Table 8a : Subroutines and Functions (_ & A-H) and Table 8b : Subroutines and Functions (I-Z).
The main steps performed by this program are as follows:
The data is output into four files to ease data handling. Note that two different filename formats are listed here; the second names listed are older versions of the filenames.
A list of the product numbers with their contents can be found in Table 1 : MODIS Standard Ocean Products.
Each of these files contain the indicated ocean color products as well as metadata. Metadata contain auxiliary information such as the creation date, datatime, principal investigator, sensor characteristics, algorithms used, etc. These files also contain flags describing quantities such as data quality. A detailed description of these flags can be found in Table 3 : Flags. Logged status and error messages are also output.
The data format of the output files is HDF-EOS. These files can be read using standard HDF processing tools.
This program calculates level 2 sea-surface temperature (SST) products from level 1B satellite data. It calls the main subroutine modsstmain which calls the remaining subroutines. An ordered list of the main called routines can be found in Table 10 : MODSST Components. This program is run for every 5 minutes of satellite data, day and night (288 runs/day).
| NOTE : Because of budget constraints, the amount of MODIS realtime processing that can occur within the first 6 months may be limited. To meet these constraints, the amount of processing MAY initially be limited to every 2nd pixel. If needed, this compromise will be reflected in the code. |
The input files required for processing of SST data are:
The first five files are obtained from the satellite data itself. The ancillary data are obtained from external files as described in the Ancillary Data section above. Supplemental ancillary data required is oi.mean.bias.* which contains weekly Reynold's SST data, and can be obtained weekly via anonymous ftp to nic.fb4.noaa.gov from the directory /pub/ocean/clim1/oiupdate.
The relevant process control file is PGE10.pcf. A brief description of a PCF is given in the PCF section above.
The relevant MCFs for the MODSST routine are: MOD28L2.mcf and MOD28QC.mcf.
A brief description of an MCF is given in the MCF section above.
This routine outputs 2 files. Where two alternative filenames are listed, the second filename is an older filename format that was used :
Each of these files contain the indicated ocean color products as well as metadata. Metadata contain auxiliary information such as the creation date, datatime, principal investigator, sensor characteristics, algorithms used, etc. These files also contain flags describing quantities such as data quality. A detailed description of these flags can be found in Table 3 : Flags. Logged status and error messages are also output.
The data format of the output files is HDF-EOS. These files can be read using standard HDF processing tools.
This program is the space-binning program. After each MODCOL or MODSST run, MSBIN bins the data into equal-area space bins (see ATBD 26 by Evans) according to geographic location. Note that bad data pixels and land pixels are not space binned. When data points of different quality occur within the same grid, only the best quality data are binned. An ordered list of the main called routines can be found in Table 13 : MSBIN Components.
The output files are divided by product, data-day (see ATBD 26 by Evans), and ascending and descending tracks, a total of up to 3 data files per product for the SST data, and 2 data files per product for the ocean color data. Hence, for the 36 ocean color products, there are potentially 72 output files per granule of satellite data, with filenames of the form MODOCBxx*, where xx is the parameter number (01 to 36). For the 4 SST products, there are potentially 12 output files, with filenames of the form MOD28Bxy*, where x=D or N (day or night) and y=1 or 2. The separation of data into these files is required before the time binning program (MTBIN) can proceed.
This program is the time-binning program. It can be run after a data-day's worth of satellite data has been processed by MSBIN. It can be used to time bin the data into scales of an orbit, a day, 8 days and 24-days (and in the future it will also calculate monthly averages). The orbital and daily averages are calculated by averaging the space-binned satellite granules for each product. The 8-day averages are made by averaging the daily data, and the 24-day averages are made by averaging the 8-day data. The 8-day and 24-day averages are calculated every 8 days. The number of input files used (and their filenames) is set in the PCF file in the appropriate mtbin directory (eg. PGE49.pcf). The MCF files used have filenames of the form product##.mcf, where "product" can be MOD28A, MODOCA, etc, and ## is the parameter number (see Table 11 : MODIS Ocean Parameters). Only the best quality data are binned. An ordered list of the main called routines can be found in Table 14 : MTBIN Components. Note that this routine works best if only 24 or fewer files are input at a time. If the number of input files exceeds 24, the input files are grouped into sets of 24, and then the groups are time-binned together. The output files have names of the form MODOCtxx* or MOD28txx*, where xx is the parameter number (01-36 or D1, D2, N1, N2), and t represents the time binning resolution (A (one day), E (8 days), F (24 days) or W (declouded 8 day)).
This program is used to fill in data gaps (caused by missing or poor data) to allow the calculation of 24-day references for use in MODIS ocean processing. Land and shallow water masks are required as input. 24-day reference products are estimated from 24-day averaged products output from MTBIN by calculating smoothed, distance-weighted averages of surrounding pixels. The calculation is made every 8 days. The output references from this program (one per product) are used as input in MCLOUD. An ordered list of the main called routines can be found in Table 15 : MFILL, MCLOUD, MMAP, and MSPC Components. The output files have names of the form MODOCRxx* or MOD28Rxx*, where xx is the parameter number.
MCLOUD compares the 24-day reference data (output from MFILL) with the daily-averaged products (output from MTBIN). This comparison is used to flag data from the daily files that differ substantially from the 24-day reference values. One file per product is output per day. This program is run every day, comparing data from individual days within the center 8 days of the 24-day period (days 9-16) with the corresponding 24-day reference. An ordered list of the main called routines can be found in Table 15 : MFILL, MCLOUD, MMAP, and MSPC Components. The output files have names of the form MODOCDxx* or MOD28Dxx*, where xx is the parameter number.
The routine MSPC changes the resolution of binned files. For example, it can convert 4-km binned data to 9-km binned data by summing 4-km binned files. An ordered list of the main called routines can be found in Table 15 : MFILL, MCLOUD, MMAP, and MSPC Components. The output files have names of the form MODOCFxx* or MOD28Fxx*, where xx is the parameter number.
MMAP is used to map level 3, equal-area binned data into their geographic projections using the HDF-EOS geographic grid, creating level 4 data (mapped statistics). The resolutions currently created are: 1 degree (360 x 180 global map), 4 km (8192 x 4096 global map), 9 km (4096 x 2048), and 36 km (1024 x 512 global map). An ordered list of the main called routines can be found in Table 15 : MFILL, MCLOUD, MMAP, and MSPC Components. The output files have names of the form MOrrstxx, where rr is the resolution (04, 36, or 1D for 4 km, 36 km and 1 degree, respectively), s is the mapped values (M (mean), S (standard deviation), N (number of pixels per bin), Q (quality), F (common flags), 1 (flag byte 1), 2 (flag byte 2) or 3 (flag byte 3)), t is the file type (A (interim daily), D (permanent daily) or W (declouded 8 day)), and xx is the parameter number.
Documented by Jasmine S. Bartlett, COAS, Oregon State University.