This page is under construction...explanation and links will be added in the coming days and weeks...feedback welcome!
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As of version 4.5.2, the netCDF Operator ncks generates SCRIP-format gridfiles for select grid types, including uniform/equi-angular, cap/FV, and Gaussian rectangular latitude/longitude grids. Full documentation is at http://nco.sf.net/nco.html#grid. For convenience, we sumarrize that functionality here. Options pertinent to the grid geometry and metadata are passed to NCO via key-value pairs prefixed by "--rgr". Pass at least six key-value pair arguments to create a fully explicitly specified, well-annotated grid. The six arguments, and their corresponding keys in parentheses, are: grid title (grd_ttl), filename to write the grid to (grid), number of latitudes (lat_nbr), number of longitudes (lon_nbr), latitude grid type (lat_typ), and longitude grid type (lon_typ). Four other arguments (the NSEW bounding box) are necessary to construct regular regional (non-global) grids, but for now we focus on global grids.
The lat_typ options for global grids are "uni" for Uniform-angle (currently same as "eqa" for Equi-angular in latitude), "cap" for Cap (same as "fv" for Finite Volume scalar grid in the Lin-Rood representation), and "gss" for Gaussian. A uniform Uniform (or equi-angular) in-latitude grid has constant spacing in latitude, and may have any number of latitudes. No points are centered at the poles in a Uniform-latitude grid. An A Cap grid is nearly identical to a Uniform-latitude grid, with some important data and metadata differences at the poles. Cap grids (aka FV-scalar grids) are rectangular representations of Uniform-latitude grids that have a "cap" point at each pole. In order to add-up to the same latitude across the cap-point as in the rest of the zones, the polar cells in the Cap rectangular representation on disk must span half the width of the other latitudes. Moreover, that is why the center and outer interface of the polar points in the Cap grid are both labeled as 90 degrees. Gaussian The contents of the polar latitude rows are often assumed to be uniform and aggregable into single "cap points" in memory. Gaussian grids must have an even number of latitudes, and therefore never have points centered on the Equator or at the poles. The lon_typ options for global grids are "grn_ctr" and "180_ctr" for the first gridcell centered at Greenwich or 180 degrees, respecitvely. And "grn_wst" and "180_wst" for Greenwich or 180 degress lying on the western edge of the first gridcell.
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