POP Grid to Lat/Lon Grid

The conversion of lat/lon grids to the POP grid is limited by the existence of the grid files and the associated weight files. Weight files for climate validated configurations are freely available for download from the Earth System Grid (ESG). More details are available here.

NCL version 4.2.0.a032 or later requires the user to set an environment variable to point to the location of the map and grid files required for remapping. This change was necessary because of the creation of two separate libraries of these files both inside and outside the NCAR supercomputing firewall. 
    setenv  NCL_POP_REMAP /fis/cgd/cseg/csm/mapping/maps
The translation coefficients used to interpolate from the POP to the lat/lon grid were developed to strictly apply to the surface only. The coefficients were developed so that the ocean and atmosphere models could communicate. The topography reflects the surface only. If you try and plot a level deeper than the surface, you may get errors around boundaries (continents) since the surface topography is not necessarily applicable with depth. If you wish to plot a layer other than the surface, it may be possible to run SCRIP with a different topography file. We are not aware of anyone who has done this however, and do not know the procedures.
pop2lat_1.ncl:

Uses PopLatLon() to convert the pop grid to a lat/lon grid.

The arguments are:
  • variable e.g. "T"
  • original grid name e.g. "gx3"
  • output grid name e.g. "T62"
  • weight method e.g. "bilin" or "aave" for bilinear or area averaged
  • type of weights e.g. "da", for destarea, or "fa"
  • time on grid file
pop2lat_2.ncl:

Uses PopLatLonV() to convert the vectors on the pop grid to a lat/lon grid.

The arguments are the same as example 1 above except that we pass in u and v.
pop2lat_3.ncl:

A slice plot. After converting to a regular grid, coordinate subscripting can be used to select a specific latitude or longitude.