UTL-NCF

Structure of Blocks

FOR EACH SIMULATION

    BEGIN OPTIONS
      [WKT <wkt>]
      [CRS_WKT <crs_wkt>]
      [DEFLATE <deflate>]
      [SHUFFLE]
      [CHUNK_TIME <chunk_time>]
      [CHUNK_FACE <chunk_face>]
      [CHUNK_Z <chunk_z>]
      [CHUNK_Y <chunk_y>]
      [CHUNK_X <chunk_x>]
      [MODFLOW6_ATTR_OFF]
    END OPTIONS

    BEGIN DIMENSIONS
      [NCPL <ncpl>]
    END DIMENSIONS

    BEGIN GRIDDATA
      [LATITUDE
            <latitude(ncpl)> -- READARRAY]
      [LONGITUDE
            <longitude(ncpl)> -- READARRAY]
    END GRIDDATA

Explanation of Variables

Block: OPTIONS

  • wkt is the coordinate reference system (CRS) well-known text string in WKT1 format (OGC 01-009). Written as the wkt attribute on the projection variable. Ignored when latitude and longitude griddata arrays have been provided. To also embed the CRS in the binary grid file, provide the same string as the CRS option in the discretization input; the discretization CRS option additionally accepts other pyproj-compatible identifiers such as an EPSG code (e.g. EPSG:26918).

  • crs_wkt is the coordinate reference system (CRS) well-known text string in WKT2 format (ISO 19162:2019), as required by CF-1.11. Written as the crs_wkt attribute on the projection variable. When omitted, the wkt value is written to crs_wkt as a compatibility alias. Ignored when latitude and longitude griddata arrays have been provided. To also embed the CRS in the binary grid file, provide the same string as the CRS option in the discretization input; the discretization CRS option additionally accepts other pyproj-compatible identifiers such as an EPSG code (e.g. EPSG:26918).

  • deflate is the variable deflate level (0=min, 9=max) in the NetCDF file. Defining this parameter activates per-variable compression at the level specified. Use with the SHUFFLE option to also enable the shuffle filter.

  • SHUFFLE is the keyword used to turn on the NetCDF variable shuffle filter when the deflate option is also set. The shuffle filter has the effect of storing the first byte of all of a variable’s values in a chunk contiguously, followed by all the second bytes, etc. This can be an optimization for compression with certain types of data.

  • chunk_time is the chunk size for the time dimension in a NETCDF_MESH2D or NETCDF_STRUCTURED output file. Must be used in combination with the chunk_face parameter (NETCDF_MESH2D) or the chunk_z, chunk_y, and chunk_x parameter set (NETCDF_STRUCTURED) to have an effect.

  • chunk_face is the keyword used to provide a data chunk size for the face dimension in a NETCDF_MESH2D output file. Must be used in combination with the the chunk_time parameter to have an effect.

  • chunk_z is the chunk size for the layer (vertical) dimension in a NETCDF_STRUCTURED output file. Must be used in combination with the chunk_time, chunk_x, and chunk_y parameters to have an effect.

  • chunk_y is the chunk size for the y dimension in a NETCDF_STRUCTURED output file. Must be used in combination with the chunk_time, chunk_x, and chunk_z parameters to have an effect.

  • chunk_x is the chunk size for the x dimension in a NETCDF_STRUCTURED output file. Must be used in combination with the chunk_time, chunk_y, and chunk_z parameters to have an effect.

  • MODFLOW6_ATTR_OFF is the keyword used to turn off internal input tagging in the model NetCDF file. Tagging adds internal modflow 6 attribute(s) to variables which facilitate identification. Currently this applies to gridded arrays.

Block: DIMENSIONS

  • ncpl is the number of cells in a projected plane layer.

Block: GRIDDATA

  • latitude cell center latitude array. Only supported for NETCDF_STRUCTURED export type. Providing latitude and longitude arrays enables geographic-coordinate output as a special case for external tooling that requires it; the preferred approach is to use the wkt and crs_wkt options instead. When latitude and longitude arrays are provided, any wkt or crs_wkt option values are ignored.

  • longitude cell center longitude array. Only supported for NETCDF_STRUCTURED export type. See the latitude description for usage notes.

Example Input File

    BEGIN OPTIONS
      DEFLATE 5
      SHUFFLE
      CHUNK_TIME 10
      CHUNK_FACE 19690
      WKT 'PROJCS["NAD_1983_UTM_Zone_14N",GEOGCS["GCS_North_American_1983",DATUM["D_North_American_1983",SPHEROID["
    GRS_1980",6378137.0,298.257222101]],PRIMEM["Greenwich",0.0],UNIT["Degree",0.0174532925199433]],PROJECTION["Transver
    se_Mercator"],PARAMETER["False_Easting",500000.0],PARAMETER["False_Northing",0.0],PARAMETER["Central_Meridian",-99.
    0],PARAMETER["Scale_Factor",0.9996],PARAMETER["Latitude_Of_Origin",0.0],UNIT["Meter",1.0]]'
    END OPTIONS