6. Regridding
Users who wish to interpolate their UPP output to a different grid may do so with the wgrib2 utility. The general format for re-gridding to various common projections are outlined in the following examples.
Wgrib2 is a versatile program that has the ability to convert grib2 files from one grid to another for various user-defined grids as well as pre-defined NCEP grids. Complete documentation with examples of re-gridding for all available grid definitions can be found at: http://www.cpc.ncep.noaa.gov/products/wesley/wgrib2/new_grid.html
6.1. Examples of wgrib2
Example 1: Latitude-Longitude Grid
-new_grid latlon lon0:nlon:dlon lat0:nlat:dlat outfile
Variable |
Description |
|---|---|
lon0 |
Longitude of first grid point in degrees |
nlon |
Number of longitudes |
dlon |
Grid resolution in degrees of longitude |
lat0 |
Latitude of first grid point in degrees |
nlat |
Number of latitudes |
dlat |
Grid resolution in degrees of latitude |
Example 2: Lambert Conic Conformal Grid
-new_grid lambert:lov:latin1:latin2 lon0:nx:dx lat0:ny:dy outfile
Variable |
Description |
|---|---|
lov |
Longitude where y-axis is parallel to meridian in degrees |
latin1 |
First latitude from pole which cuts the secant cone in degrees |
latin2 |
Second latitude from pole which cuts the secant cone in degrees |
lon0 |
Longitude of the first grid point in degrees |
nx |
Total number of grid points along x |
dx |
Grid cell size in meters in x direction |
lat0 |
Latitude of the first grid point in degrees |
ny |
Total number of grid points along y |
dy |
Grid cell size in meters in y direction |
Example 3: Polar Stereographic Grid
-new_grid nps:lov:lad lon0:nx:dx lat0:ny:dy outfile
OR
-new_grid sps:lov:lad lon0:nx:dx lat0:ny:dy outfile
Variable |
Description |
|---|---|
nps/sps |
North/south polar stereographic |
lov |
Longitude where y-axis is parallel to meridian in degrees |
lad |
Latitude where dx and dy are specified |
lon0 |
Longitude of the first grid point in degrees |
nx |
Total number of grid points along x |
dx |
Grid cell distance in meters in x direction at lad |
lat0 |
Latitude of the first grid point in degrees |
ny |
Total number of grid points along y |
dy |
Grid cell distance in meters in y direction at lad |
Winds
-new_grid_winds grid OR -new_grid_winds earth
Variable |
Description |
|---|---|
grid |
U-wind goes from grid (i,J) to (i+1,j) |
earth |
U-wind goes eastward, V-wind goes northward |
Interpolation
The default interpolation type is bilinear, but it can be set to another type (e.g., neighbor, budget).
-new_grid_interpolation type
Operational Example
Interpolates to a 0.25 degree latitude-longitude grid using various interpolation types depending on the variable.
wgrib2 infile -set_grib_type same -new_grid_winds earth |
-new_grid_interpolation bilinear |
-if ":(CRAIN|CICEP|CFRZR|CSNOW|ICSEV):" -new_grid_interpolation neighbor -fi |
-set_bitmap 1 -set_grib_max_bits 16 |
-if ":(APCP|ACPCP|PRATE|CPRAT):" -set_grib_max_bits 25 -fi |
-if ":(APCP|ACPCP|PRATE|CPRAT|DZDT):" -new_grid_interpolation budget -fi |
-new_grid "latlon 0:1440:0.25 90:721:-0.25" outfile
Note
wgrib2 is not distributed as part of the UFS, but it can be installed via HPC-Stack or spack-stack along with other UFS prerequisite software. Users may also download and install it directly from http://www.cpc.ncep.noaa.gov/products/wesley/wgrib2/.