LatLon2DGridDescriptor

A descriptor for 2D latitude-longitude grids.

Overview

The LatLon2DGridDescriptor class is used for grids where latitude and longitude are defined as 2D arrays.

Attributes

• lat_2d: 2D array of latitude values.

• lon_2d: 2D array of longitude values.

Methods

• read: Reads a 2D latitude-longitude grid from a file.

• to_scrip: Converts the grid to a SCRIP file.

Grid-Cell Corners

As with LatLonGridDescriptor, read() uses the CF bounds of the latitude and longitude variables to find grid-cell corners when they are available. For 2D coordinates, the bounds give the 4 vertices of each cell:

double lat(y, x) ;
    lat:units = "degrees_north" ;
    lat:bounds = "lat_bnds" ;
double lat_bnds(y, x, nv) ;

CF does not say which vertex comes first or which direction the 4 vertices are traversed in, so pyremap works this out from the bounds themselves. Both latitude and longitude must have bounds, and neighboring cells must share vertices, since the grid is described by 2D arrays of corners. Otherwise, corners are interpolated and extrapolated from cell centers and a warning is raised.

Example

from pyremap import LatLon2DGridDescriptor

descriptor = LatLon2DGridDescriptor.read("grid.nc")
descriptor.to_scrip("grid.scrip.nc")