NARR data is distributed on a native lambert conformal grid with 2D latitudes and longitudes. For a description of native lambert conformal grids and how to plot them accurately in NCL, click here, or refer to any of the examples below.
NARR data is available from NCAR's Data Support Section in GRIB format, a subset of NARR data is also available from the Climate Diagnostics Center (CDC) in netCDF format. See Example 2.
narr_1.ncl:
This script demonstrates how to quickly read a NARR GRIB
file into NCL, and shows how to plot the data on the NARR native grid.
Note that NCL can read GRIB files directly. In addition, NCL provides additional information [eg, geographical coordinates] that are not on the original GRIB formatted file. The ncl_filedump utility can be used to view any GRIB [nc, hdf-sds, hdf-eos] file as seen via NCL.
narr_2.ncl:
This script demonstrates how to read in a NARR netCDF file into NCL. In this case, the data
is stored as 16-bit integers (referred to as type "short"). In general, data of type short
must be transformed prior to calculations and plotting . The contributed function
short2flt may be used to directly read the data. Note
that short2flt will automatically apply the add_offset and
scale_factor attributes during the conversion from short to float.
narr_3.ncl:
This script uses
the nearest neighbor function triple2grid to interpolate
from the NARR Lambert Conformal grid to a 2 degree by 2 degree grid.
The original grid is plotted in the top panel, while the regridded data is shown in the bottom panel.
Note: triple2grid was not designed for this type of application so it can be slow.
The sample script outputs a netCDF file containing the interpolated 2x2 grid. An ncl_filedump of the netCDF file is here.
narr_4.ncl:
This does an interpolation to a regular 2x2 grid like Example 3.
Then, using the (lat,lon) pairs specified by the user, it
calculates the great circle path between the specified points using gc_latlon.
Finally, interpolate the 2x2 grid to the great circle transect using
linint2_points.
Note_1: The great circle pat was used for convenience. However, the user could specifiy any set of (lat,lon) pairs and input these directly to linint2_points.
Note_2: triple2grid was not designed for this type of application so it can be slow. In some applications it may be best to create a netCDF file [see Example 3] and then read the file.