JISAO data

GrADS command lines for reading COARDS netCDF files

The Grid Analysis and Display System (GrADS) analyses and displays gridded data. GrADS can ingest netCDF-format files by three methods, the simplest of which is with the routine "sdfopen" (GrADS documentation). Files that are compliant with the COARDS (Cooperative Ocean / Atmosphere Research Data Service) standards can be ingested with "sdfopen filename.nc" (no quotes). If this doesn't work for you, it may be because the time variable is written in different time units than what sdfopen has been written to handle. sdfopen used to only take files where time was written in hours. I am not sure if it is more flexible now.

In the example that follows, the input file to be read is entitled "slp.mon.mean.nc".

To open a file, once you are in GrADS, just type:

-> sdfopen slp.mon.mean.nc

This command will open the file, and give you the ranges of the
dimensions of the file.  To see what the variable name is, type

-> q file 1

and it will return

File 1 : monthly mean slp from the NCEP Reanalysis
  Descriptor: slp.mon.mean.nc
  Binary: slp.mon.mean.nc
  Type = Gridded
  Xsize = 144  Ysize = 73  Zsize = 1  Tsize = 752  Esize = 1
  Number of Variables = 1
     slp  0  t,y,x  Sea Level Pressure

The variable name is "slp."  To plot the second month of data

-> set t 2

-> d slp
The GrADS WWW home page documents the GrADS commands, and there is a short and useful tutorial.

December 2010
Todd Mitchell (mitchell@atmos.washington.edu)
JISAO data