Thursday, May 2, 2013

Introduction to GrADS

Hello!  I am starting this blog because throughout my undergraduate and graduate career in meteorology and atmospheric science, I have developed a hearty knowledge of the free Grid Analysis Display System (or GrADS) software package.  Most of my skills come from trial and error, as well as what I like to call "precision Googling."  After acquiring these skills, I feel as if I have something to contribute to the science community. 

In a nutshell, this blog is basically my attempt to provide everyone with a lot of the tools and tips that I wish I had while I was learning/using GrADS.  I welcome feedback and questions related to this blog, and GrADS in general.  It is my sincerest hope that keeping up with this blog serves both to help GrADS users with a variety of different GrADS challenges and to help grown my own knowledge and abilities with GrADS.

So lets start with the basics, below is a list of advantages and disadvantages to using the software.

  • Free/Easy to install
  • Works well on Windows
  • Easy to learn scripting/good introduction into computer programming
  • Quick and easy access to real time and reanalysis weather data through interface
  • Capability of both reading and writing shape files
  • Possible to develop GUI interface using scripting Language
  • KML/PNG/JPG/GIF/TXT/DAT file output
  • Large library of scripts available online
  • Does not use a ton of memory
  • Models such as WRF and the Bryan Cloud Model (CM1) include GrADS output options
  • Works with both gridded and station datasets
  • Handles binary, NetCDF, HDF5, grib, grib2 file types
  • Pretty darn fast!
  • Not as powerful as other plotting software (e.g., Python, NCL)
  • Relatively low quality images (compared to Matlab,Python, etc., at least in my opinion)
  • Cannot easily perform high level data functions such as EOF analysis
  • Cannot easily plot "Generic vertical cross sections" (that is anything other than East/West or North/South)
If you are still wondering if GrADS is right for you, I included a few example images made with GrADS to give you an idea of what GrADS can be used for.

Visible Satellite Data and Counties
Surface weather map from the NAM model

NARR Reanalysis Precipitable Water

So, now that you have an idea of what to expect with GrADS, I will provide a few links and some basic info so you can get started.  Now, I presume if you are here you probably have GrADS installed on your computer and you probably are just looking for a few scripts to help you make some bad-ass weather plots.  I highly doubt you just stumbled across this in your spare time and decided to get started with GrADS based on the information in this post, but just in case you did here is a paragraph describing how to install the software.

So the first thing you will want to do is get the GrADS software installed on your computer.  As I recall, installing the software was as easy as going to This Website and downloading the version you want, untarring/unzipping the folder, and installing it.  Note, if you are using windows you will need Cygwin installed, however, if I recall correctly, it comes as part of the GrADS package available for windows, so this should be fairly straight forward.  The installation comes with a bunch of different executable files (all listed on the website).

In windows you can open the GrADS interface by double-clicking the executable file (linux just typing "grads" into your console should do the trick).  GrADS first opens a command shell and prompts you to choose "landscape" or "portrait" for your image dimensions (the default is landscape).  Once you make your choice, a second window will open up.  This window will be where your data is plotted.  So basically, you have a command console to enter commands, and a display console where your data will be plotted.  Once you have these windows up, all that's left is to learn the commands!

Now instead on going through a detailed instruction on how to use commands in GrADS, I am going to go ahead and point anyone new to GrADS to This Tutorial to help get you started.  This is just because I don't want to repeat a ton of information that is already widely available from other places.  Anyway, once you have gone through the tutorial and have a basic idea of the different functions you can use with GrADS, I encourage you to come back here and browse the different scripts/tutorials I have put on this blog.

So I think that's it for the introduction, I hope you found this post useful and please check back soon for new scripts/tutorials!


  1. There's a function you can download to perform EOF on Grads.

  2. Are you sure? I thought I had read that UDFs were discontinued for versions 2.0 and greater. Though, if you can still get that function working that is fantastic news! Let me know, I'd be interested in getting something like that working.