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gridspec

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Gridspec is a proposed standard for representing Earth system model grids. The standard was originally proposed by V. Balaji and Z. Liang (2007; reference).

Gridspec files are useful for offline regridding with the Earth System Modeling Framework (ESMF), but there are no generalized frameworks or utilities for creating gridspec files and data. This project aims to develop common tools for working with gridspec files and data.

Supported grids

The grids that are currently implemented are:

  • gnomonic cubed-sphere (see: gridspec-create gcs --help)
  • stretched gnomonic cubed-sphere (see: gridspec-create sgcs --help)
  • regular lat-lon grid (see: gridspec-create latlon --help)
    • pole-centered/polar-edge and dateline-centered/dateline-edge
    • regional lat-lon grid
  • gaussian grid

See "Contributing" for information on submitting pull-requests and setting up a development copy.

Compliance

  • ESMF GRIDSPEC (subset of the standard)
  • Full gridspec standard

Installation

You can install gridspec like so:

$ pip install git+https://github.com/LiamBindle/gridspec.git

This installs (see --help for subcommands and their usage):

  • gridspec-create: create a gridspec file for one of the supported grids (mosaic or tile)
  • gridspec-dump: displays useful information about a gridspec file
  • gridspec-utils: utilities for working with gridspec data (splitting stacked data files, joining tiled data files, etc.)

Examples

Creating a cubed-sphere grid:

$ gridspec-create gcs 24
Creating gnomonic cubed-sphere grid.
  Cubed-sphere size: C24

Writing mosaic and tile files
  + c24_gridspec.nc
  + c24.tile1.nc
  + c24.tile2.nc
  + c24.tile3.nc
  + c24.tile4.nc
  + c24.tile5.nc
  + c24.tile6.nc

Created 7 files.
$

Creating a stretched cubed-sphere grid:

$ gridspec-create sgcs 24 -s 2 -t 40 -100
Creating stretched gnomonic cubed-sphere grid.
  Cubed-sphere size: C12
  Stretch factor:    2.0
  Target point:      40.0°N, -100.0°E

Writing mosaic and tile files.
  + c12_s2d00_t9z0gs3y0zh7w_gridspec.nc
  + c12_s2d00_t9z0gs3y0zh7w.tile1.nc
  + c12_s2d00_t9z0gs3y0zh7w.tile2.nc
  + c12_s2d00_t9z0gs3y0zh7w.tile3.nc
  + c12_s2d00_t9z0gs3y0zh7w.tile4.nc
  + c12_s2d00_t9z0gs3y0zh7w.tile5.nc
  + c12_s2d00_t9z0gs3y0zh7w.tile6.nc

Created 7 files.
$

View the contents of a mosaic or tile file:

$ gridspec-dump c24_gridspec.nc                  
Gridspec mosaic  (c24_gridspec, 6 tiles, 12 contacts)
Tile files:      "c24.tile1.nc", "c24.tile2.nc", "c24.tile3.nc", "c24.tile4.nc",
...              "c24.tile5.nc", "c24.tile6.nc"

Gridspec tiles:
  tile1       (49x49)      logical center (  0.0°N, 350.0°E)    approx area: 8.5e+07 km+2
  tile2       (49x49)      logical center (  0.0°N,  80.0°E)    approx area: 8.5e+07 km+2
  tile3       (49x49)      logical center ( 90.0°N, 350.0°E)    approx area: 8.5e+07 km+2
  tile4       (49x49)      logical center (  0.0°N, 170.0°E)    approx area: 8.5e+07 km+2
  tile5       (49x49)      logical center (  0.0°N, 260.0°E)    approx area: 8.5e+07 km+2
  tile6       (49x49)      logical center (-90.0°N,  35.0°E)    approx area: 8.5e+07 km+2
$

Contributing

Submit pull requests to https://github.com/LiamBindle/gridspec. Please make sure to include tests for your PR.

To set up a developement copy:

  1. Clone the repo 
    $ git clone https://github.com/LiamBindle/gridspec
  2. Install as an editable package: 
    $ pip install -e gridspec/

Tests

To run the tests, you need to install pytest. Once pytest is installed, you can run the tests like so (pytest test discovery is described here):

$ pytest