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NOTICE: This version of the NSF Unidata web site (archive.unidata.ucar.edu) is no longer being updated.
Current content can be found at unidata.ucar.edu.
To learn about what's going on, see About the Archive Site.
Mike,I have another option which may or may not be easier or preferred to Rich's solution. I have an NCL script which creates CF compliant NetCDF files from native wrfout files. This script can be downloaded from the WRF-ARW Utility page (wrfout_to_cf.ncl at the bottom of the page):
http://www.mmm.ucar.edu/wrf/users/utilities/util.htmThe NCL script allows you to select the fields to be included in the CF file as well as to put the data on pressure levels. The script is reasonably easy to run even if you have not used NCL much.
Once the wrfout files have been converted to CF compliant NetCDF files they can be easily handled and concatenated with NetCDF Operators (NCO) utilities. This would allow you to combine several files into one NetCDF file for use in IDV.
Mark Rich Signell wrote:
Mike, On Mon, Jan 26, 2009 at 12:18 PM, Mike Leuthold <leuthold@xxxxxxxxxxxxxxxx> wrote:I've recently begun to explore IDV in order to visualize WRF output and I have the same issue that Don Morton wrote about in2006, which is that I'd like open multiple netCDF output files and be able to loop through them. The solutions at the time were to use netCDF Markup Language aggregation or cat grib files. Has there been any work on using multiple netCDF output files in IDV or am I totally missing this advance?It's pretty easy to generate the NcML to do the aggregation. Say you have two files you want to aggregate in time are called "wrf_2008021300.grib" "wrf_2008021400.grib". where each file contains a forecast at 3 hourly intervals. Here are three different scenarios: 1. If both files have the same time units (e.g. "seconds since 1970-01-01" or something) and the first time step in the 2nd file follows the last time step in the 1st file, then "wrf_agg.ncml" could be this simple: <netcdf xmlns="http://www.unidata.ucar.edu/namespaces/netcdf/ncml-2.2";> <aggregation dimName="time" type="joinExisting"> <netcdf location="wrf_2008021300.grib"/> <netcdf location="wrf_2008021400.grib"/> </aggregation> </netcdf> or you could scan all the .grib files in a specified directory instead of specifying the specific names: <netcdf xmlns="http://www.unidata.ucar.edu/namespaces/netcdf/ncml-2.2";> <aggregation dimName="time" type="joinExisting"> <scan location="/Volumes/models/wrf/" suffix=".grib"/> </aggregation> </netcdf> 2. If each file has different units for time (a different time origin), as it often the case with Grib, then you can override the time variable explicitly, giving a start and increment. <netcdf xmlns="http://www.unidata.ucar.edu/namespaces/netcdf/ncml-2.2";> <aggregation dimName="time" type="joinExisting"> <netcdf location="wrf_2008021300_0000.grib"/> <netcdf location="wrf_2008021400_0000.grib"/> </aggregation> <variable name="time"> <attribute name="units" type="String" value="hours since 2008-02-13 00:00 UTC"/> <values start="0" increment="3"/> </netcdf> 3. Finally, if each file contained a 48 hour forecast, but you wanted only the 0-21 hour values from each, you could specify those values explicitly. <netcdf xmlns="http://www.unidata.ucar.edu/namespaces/netcdf/ncml-2.2";> <aggregation dimName="time" type="joinExisting"> <netcdf location="wrf_2008021300_0000.grib" coordValue=" 0 3 6 9 12 15 18 21 " /> <netcdf location="wrf_2008021400_0000.grib" coordValue=" 0 3 6 9 12 15 18 21 " /> </aggregation> <variable name="time"> <attribute name="units" type="String" value="hours since 2008-02-13 00:00 UTC"/> <values start="0" increment="3"/> </netcdf> There may be some even easier way to do it. I trust the IDV guys will speak up, if so! -Rich
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