Data and Graphics Manipulation Tools

Below is a list of tools that are freely available and can be used to very successfully manipulate model data (WRF model data, as well as other GRIB and netCDF datasets).

Converting Graphics
Design WRF model domains.
Display ungrib (intermediate) files.
netCDF data
GRIB data
Model Verification

Converting Graphics

ImageMagick

ImageMagick is a software suite to create, edit, and compose bitmap images. It can read, convert and write images in a variety of formats (over 100) including DPX, EXR, GIF, JPEG, JPEG-2000, PDF, PhotoCD, PNG, Postscript, SVG, and TIFF. Use ImageMagick to translate, flip, mirror, rotate, scale, shear and transform images, adjust image colors, apply various special effects, or draw text, lines, polygons, ellipses and B_zier curves.

The software package is freely available from, http://www.imagemagick.org. Download and installation instructions are also available from this site.

Examples of converting data with ImageMagick software:

convert  file.pdf     file.png
convert  file.png     file.bmp
convert  file.pdf     file.gif
convert  file.ras     file.png

ImageMagick cannot convert ncgm (NCAR Graphics) file format to other file formats.

 

Converting ncgm (NCAR Graphics) file format

NCAR Graphics has tools to convert ncgm files to raster file format. Once files are in raster file format, ImageMagick can be used to translate the files into other formats.

For ncgm files containing a single frame, use ctrans.

ctrans  -d sun  file.ncgm  file.ras

For ncgm files containing multiple frames, first use med (metafile frame editor) and then ctrans. med will create multiple single frame files called medxxx.ncgm

med -e '1,$ split $' file.ncgm
ctrans  -d sun_ med001.ncgm > med001.ras

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Design WRF model domains

WPS/util/plotgrids.ncl, can be used to display model domains before WPS/geogrid.exe is run.

This utility reads the domain setup from namelist.wps and creates a file that can be viewed in the format that you choose (availalbe options are in the script: x11, pdf, ps, ncgm).

Read more about this utility in Chapter 3 of the WRF Users' Guide.

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Display ungrib (intermediate) files

WPS/util/plotfmt.ncl, can be used to display intermediate files created by WPS/ungrib.exe.

If you have created intermediate files manually, it is a very good practice to use this utility to display the data in your files first before running WPS/metgrid.exe.
Note: If you plan to manually create intermediate files, refer to http://www2.mmm.ucar.edu/wrf/OnLineTutorial/Basics/IM_files/index.php for detailed information about the file formats and sample programs.

This utility reads intermediate files and creates a file that can be viewed in the format that you choose (availalbe options are in the script: x11, pdf, ps, ncgm).

Read more about this utility in Chapter 3 of the WRF Users' Guide.

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netCDF data

netCDF stands for network Common Data Form.
Most of the information below can be used for WRF netCDF data, as well as other netCDF datasets.
netCDF is one of the current supported data formats chosen for WRF I/O API.

Advantages of using netCDF?
Most graphical packages support netCDF file formats
netCDF files are platform-independent (big_endian / little_endian)
A lot of software already exists that can be used to process/manipulate netCDF data

Documentation:
http://www.unidata.ucar.edu/ (General netCDF documentation)
http://www.unidata.ucar.edu/software/netcdf/docs/user_guide.html (NETCDF User’s Guide for FORTRAN)

Utilities:
ncdump
Part of the netCDF libraries. Reads a netCDF file and prints information about the dataset. e.g.

ncdump –h file  (prints header information)
ncdump –v VAR file  (prints header information and the full field VAR)
ncdump –v Times file   (a handy way to see how many times are available in a WRF output file)

ncview
Displays netCDF data graphically. No overlays, no maps and no manipulation of data possible.
http://meteora.ucsd.edu/~pierce/ncview_home_page.html

ncBrowse
Displays netCDF data graphically. Some overlays, maps and manipulation of data are possible.
http://www.epic.noaa.gov/java/ncBrowse/

read_wrf_nc
A utility to display basic information about WRF netCDF files.

iowrf
A utility to do some basic file manipulation on WRF-ARW netCDF files.

p_interp
A utility to interpolate WRF-ARW netCDF output files to user-specified pressure levels.
You can obtain this utility from the WRF Download Page (you must be a registered user to download any code - it is free of charge).

netCDF operators
http://nco.sourceforge.net/
Stand-alone programs that can be used to manipulate data (performing grid point averaging / file differencing / file ‘appending’). The following are examples of the available operators:

      ncdiff
      Difference two file, e.g.
      ncdiff  input1.nc input2.nc output.nc

      ncrcat
      Write specified variables / times to a new file, e.g.
      ncrcat -v RAINNC wrfout* RAINNC.nc
      ncrcat -d Time,0,231 –v  RAINNC  wrfout* RAINNC.nc

      ncra
      Average variables and write to a new file, e.g.
      ncra -v OLR  wrfout* OLR.nc

      ncks (nc kitchen sink)
      Combination of NCO tools all in one (handy: one tool for multiple operations).

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GRIB data

Documentation
http://rda.ucar.edu/docs/formats/grib/gribdoc/ (Guide to GRIB 1)
http://www.nco.ncep.noaa.gov/pmb/docs/grib2/grib2_doc.shtml (Guide to GRIB2)
http://www.nco.ncep.noaa.gov/pmb/docs/grib2/GRIB2_parmeter_conversion_table.html (GRIB2 - GRIB1 parameter conversion table)

GRIB codes

It is important to understand the GRIB codes to know which fields are available in your dataset. For instance, NCEP uses the GRIB1 code 33 for the U-component of the wind, and 34 for the V-component. Other centers may use different codes, so always obtain the GRIB codes from the center from which you get your data.

GRIB2 uses 3 codes for each field - product, category and parameter.
We would most often be interested in product 0 (Meteorological products). Category refers to the type of field, e.g., category 0 is temperature, category 1 is moisture and category 2 is momentum. Parameter is the field number.
So whereas GRIB1 only uses code 33 for the U-component of the wind, GRIB2 will use 0,2,2, for the U-component, and 0,2,3 for the V-component.
 

Display GRIB header/field information

GRIB1 data
WPS/util/g1print.exe
wgrib (http://www.cpc.ncep.noaa.gov/products/wesley/wgrib.html)

GRIB2 data
WPS/util/g2print.exe
wgrib2 (http://www.cpc.ncep.noaa.gov/products/wesley/wgrib2/)
 

Convert GRIB1 data to netCDF format
ncl_grib2nc (http://www.ncl.ucar.edu/Document/Tools)

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Model Verification

MET is designed to be a highly configurable, state-of-the-art suite of verification tools. It was developed using output from the Weather Research and Forecasting (WRF) modeling system but may be applied to the output of other modeling systems, as well.

MET provides a variety of verification techniques, including:

  • Standard verification scores, comparing gridded model data to point-based observations
  • Standard verification scores, comparing gridded model data to gridded observations
  • Object-based verification method, comparing gridded model data to gridded observations

http://www.dtcenter.org/met/users/index.php

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