Concatenating FNL met data with WRF output

[John.Johansson]

I have run WRF on two nested domains using FNL metdata as input. I wanted to combine the output from the two domains and the FNL data to use as input for HYSPLIT. The idea was that the FNL data would be used outside of the WRF domains.

First I converted the FNL files from GRIB2 to GRIB1. Then I converted them from GRIB1 to the ARL format using grib2arl. Then I concatenated 4 of these files to get a file covering a whole day (FNL data has 6 hour time resolution). This file seems fine when i check it with chk_file and chk_data. Then I converted the WRF output files for each domain to the ARL format using arw2arl. These files also seem fine when I check with chk_file and chk_data. The WRF output files contain hourly data for a whole day each.

However, when I concatenate the converted daily FNL file with the two converted WRF output files I get a file that is not as well-behaved. The output from chk_file is:

Code: Select all

 ERROR metset: meteorological data time interval varies
  Changed from          360  min to        -1080  min
  At day/hr            1           0

and the output from chk_data looks fine until I get to the wborder between the two concatenated files. Then I get this output:

Code: Select all

13 8 1 099 099INDX   0 0.0000000E+00 0.0000000E+00

 ERROR: decoding header
 �z��|}�}}y��u�}�{����w{~~zz����U��}|~ox||}}z
 GFSG  0 090.0000359.0001.000001.00000.000000.000000.0000001.000001.00000-90.000.000000.000000360181 21 21276

I have also tried running test trajectories with this file, but I get the same error as from chk_file. What am I doing wrong? I thought it was possible to combine different metdata by simply concatenating the files. HYSPLIT seems to be complaining that all the data is not in chronological order, but this would be a natural effect of concatenating two files containing data for more than one time point each. Do I need to sort the data somehow?

[barbara.stunder]

To use both WRF and FNL data for a trajectory, list them both in the CONTROL file. You can use the GUI to choose the two meteorology files, run a trajectory, then you can look at the CONTROL file to see how the files are listed.

HYSPLIT meteorology files can be concatenated only if they are the same but with different valid times.

[John.Johansson]

Thank you for the fast reply!

Okay, I don't know where I got the impression that you could concatenate metdata on different grids to the same file.

This causes a different problem though, due to the limit on the number of input files listed in the CONTROL file (7 I think). I guess the solution is to concatenate data for longer time periods for each grid. But no matter how long time periods I divide the input data into, some of my trajectories will always be on the edge between two files, so I need to be able to include two files for each grid in the CONTROL file. This means I can't use more than 3 grids (of which only 2 will be WRF grids). I guess this works for what I'm doing right now, but it would be a problem if I wanted to add another WRF grid. Is there any way to get around this limitation?

[barbara.stunder]

There can be 12 input meteorology files in the CONTROL file, so that will help you some. Yes, concatenate the same grids to the extent possible. Otherwise, break apart your job into smaller pieces for each batch of meteorology files.