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A few pointers for working with CAM datasets

pjr

Member
This thread is really a test of using the bulletin board software but I will try to include a few useful pieces of information at the same
time.

I will begin by reminding the reader that all CAM datasets use the netCDF file format created by the UNIDATA group at UCAR. The format, and software to manipulate files using this format can be found at http://my.unidata.ucar.edu/content/software/netcdf/index.html.

That web site contains pointers to source code written by UNIDATA, as well as useful public domain and commercial software that can
plot, and manipulate the files created with the UNIDATA products.
It also contains a discussion of "best practices" and "conventions" for creating netCDF files that make it considerably easier to exchange files with other researchers.

The CAM uses the "CF" (Climate and Forecast Metadata) convention http://www.cgd.ucar.edu/cms/eaton/cf-metadata/index.html which facilitate exchange of data by suggesting naming conventions, units for data, etc.

The crudest program to examine a netCDF file, and one used regularly by many researchers is distributed with the UNIDATA software itself. The programs is called "ncdump". The programs is capable of tranlating netcdf files to an ASCII (text) representation. ncdump is frequently the first program used when an unfamiliar netCDF file is provided to someone, to get an idea of the contents of the file. A particularly useful form of the ncdump command uses the "-h" argument. So, for example the command

ncdump -h test.nc

would display the "metadata" associated with the netCDF file called "test.nc".

There are many many other packages mentioned on that website that provide a broad variety of ways of manipulating and examining netCDF files. Here are list of a few of my favorites:

NCO --- The netCDF Operators Suite http://nco.sourceforge.net/ is a collection of programs that allow one to sample, extract, average, and subset netCDF files very easily.

NCview: a netCDF visual browser --- http://meteora.ucsd.edu/~pierce/ncview_home_page.html provides a very easy GUI based approach to display plots of the data in a netCDF file.

NCL --- The NCAR Command Language http://ngwww.ucar.edu/ncl/ is an interpreted language sitting on top of the NCAR graphics package that make it straightforward to manipulate and display data in netCDF files.

Yorick, IDL, and HOPS --- Yorick and IDL are two powerful interpreted languages that work well with netCDF files. HOPS is a package that sits on top of Yorick or IDL that make it easy to to do relatively complicate tasks on netCDF data more easily than might otherwise occur. You will find pointers to all three programs at
http://www.cgd.ucar.edu/gds/svn/hyperslab.html

You will find an enormous number of very nice programs mentioned on the UNIDATA website.

Hope this helps you get started.

Phil Rasch
 
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