6.1. AWIPS SCMI Writer

The SCMI AWIPS writer is used to create AWIPS compatible tiled NetCDF4 files. The Advanced Weather Interactive Processing System (AWIPS) is a program used by the United States National Weather Service (NWS) and others to view different forms of weather imagery. Sectorized Cloud and Moisture Imagery (SCMI) is a netcdf format accepted by AWIPS to store one image broken up in to one or more “tiles”. Once AWIPS is configured for specific products the SCMI NetCDF writer can be used to provide compatible products to the system. The files created by this writer are compatible with AWIPS II.

The SCMI writer takes remapped image data and creates an AWIPS-compatible NetCDF4 file. The SCMI writer and the AWIPS client may need to be configured to make things appear the way the user wants in the AWIPS client. The SCMI writer can only produce files for datasets mapped to areas with specific projections:

  • Lambert Conformal Conic (+proj=lcc)

  • Geostationary (+proj=geos)

  • Mercator (+proj=merc)

  • Polar Stereographic (+proj=stere)

This is a limitation of the AWIPS client and not of the SCMI writer.

6.1. Numbered versus Lettered Grids

By default the SCMI writer will save tiles by number starting with ‘1’ representing the upper-left image tile. Tile numbers then increase along the column and then on to the next row.

By specifying --letters on the command line, tiles can be designated with a letter. Lettered grids or sectors are preconfigured in the SCMI writer configuration file (scmi_backend.ini). The lettered tile locations are static and will not change with the data being written to them. Each lettered tile is split in to a certain number of subtiles (–letter-subtiles), default 2 rows by 2 columns. Lettered tiles are meant to make it easier for receiving AWIPS clients/stations to filter what tiles they receive; saving time, bandwidth, and space.

Any tiles (numbered or lettered) not containing any valid data are not created.


The SCMI writer does not default to using any grid. Therefore, it is recommended to specify one or more grids for remapping by using the -g flag.

6.1.1. Command Line Arguments

usage: polar2grid.sh <reader> scmi [-h]
                                   [--backend-configs [BACKEND_CONFIGS [BACKEND_CONFIGS ...]]]
                                   [--compress] [--fix-awips]
                                   [--tiles TILE_COUNT TILE_COUNT]
                                   [--tile-size TILE_SIZE TILE_SIZE]
                                   [--letter-subtiles LETTER_SUBTILES LETTER_SUBTILES]
                                   [--output-pattern OUTPUT_PATTERN]
                                   [--source-name SOURCE_NAME] --sector-id

6.1. Backend Initialization


alternative backend configuration files


zlib compress each netcdf file

Default: False


modify NetCDF output to work with the old/broken AWIPS NetCDF library

Default: False

6.1. Backend Output Creation


Number of tiles to produce in Y (rows) and X (cols) direction respectively

Default: [1, 1]


Specify how many pixels are in each tile (overrides ‘–tiles’)


Create tiles from a static letter-based grid based on the product projection

Default: False


Specify number of subtiles in each lettered tile: ‘row col’

Default: (2, 2)


output filenaming pattern

Default: “{source_name}_AII_{satellite}_{instrument}_{product_name}_{sector_id}_{tile_id}_{begin_time:%Y%m%d_%H%M}.nc”


specify processing source name used in attributes and filename (default ‘SSEC’)

Default: “SSEC”


specify name for sector/region used in attributes and filename (example ‘LCC’)

6.1.2. Lettered Sectors


polar2grid.sh acspo scmi --letters --compress -g lcc_conus_300 --sector-id LCC  --grid-coverage=0.0 -f 20170717185500-STAR-L2P_GHRSST-SSTskin-MODIS_T-ACSPO_V2.40-v02.0-fv01.0.nc

polar2grid.sh clavrx scmi --sector-id Polar --letters --compress -g polar_alaska_700 -p refl_lunar_dnb_nom cloud_phase cld_height_acha --grid-coverage=0.0 -f /data/clavrx_npp_d20170706_t0806562_e0808204_b29481.level2.hdf

polar2grid.sh viirs_sdr scmi -g merc_pacific_1km --sector-id Pacific --letters --compress -f /path/to/files*.h5