[Met_help] More data interpolation problems

[John Halley Gotway]

Steve,

I didn't get the attachment to this message, but actually I think I know what's going on.  And it's a problem that we're aware of.  This bug is fixed in the development version of MET for version 2.0,
but not fixed in METv1.1.  The fix is logically very simple, but it affects a whole bunch of files because we need to pass additional information to library sub-routines.

Here's what going on...
In the configuration file, you may indicate that you'd like to look at the U-component of winds at 10 meters by specifying "UGRD/Z10".  Currently, MET reads that in looks for a record in the GRIB file
that contains UGRD with a level value of 10.  However, your GRIB file contains 2 records with a level value of 10.  In the sample file you sent me before (named wrf_d01_easia_200712130000.grb), record
67 contains UGRD at 10mb and record 671 contains UGRD at 10 meters.

When MET sees that record for 10mb, it's using that instead of the 10m winds you actually want!

The fix is to be smarter about how we match records, and make use of the "Z" that you specified in the config file.  We need to read the level type for each record and are able to differentiate
between pressure levels and vertical levels.

For a short-term work-around, you could use the following copygb command to extract only the vertical-level type records from your files:
copygb -k'5*-1 105' -x  wrf_d01_easia_200712130000.grb vert_level_vars.grb

That pulls out all the GRIB records with the level indicator equal to a value of 105.  A value of 105 means "specified height level above ground in meters" (taken from
http://www.nco.ncep.noaa.gov/pmb/docs/on388/table3.html).

If you extract these records to a separate file and then run them though MET looking for Z10, it'll grab the field you want.  Alternatively, you could turn off the output of 10mb winds from WPP.

Will that meet your needs until METv2.0 is ready in February 2009?

Sorry for the confusion.

Thanks,
John

Masters.Steve wrote:
> The fix that you recently posted appears to have fixed the wind
> rotation/interpolation problem for upper air data.  However, I am still
> getting erroneous WRF winds when trying to verify surface observations.
> I've attached at tar file that illustrates the problem.  This job was
> run using the same WRF run that I used last week when describing the
> problem with the upper air data.   The WRF winds appear to be much too
> strong, and do not match the 10 m AGL winds that I get when I use grads
> to examine the data.
> 
> Interestingly, the UGRD and VGRD/Z10 winds that come from the point_stat
> program seem to closely match the 10 hPa winds I pull using grads.  It
> seems like my variable/level specification is not being interpreted
> correctly.
> 
> Steve Masters  masters.steve at ensco.com
> ENSCO, Inc.
> Melbourne, FL
> 
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