[Met_help] MET questions

[John Halley Gotway]

Cory,

Thanks for catching that!  I'll update the comments in the config files.

John

Cory Davis wrote:
> Thanks John, thats great.  can I suggest a change in the example
> PointStatConfig file? 
> 
> line 21:
> 
> //    GC/ZNNN for vertical level NNN (may only be set to 2 or 10)
> 
> 
> Cheers,
> Cory.
> 
> On Wed, 2008-01-23 at 14:46 -0700, John Halley Gotway wrote:
>> Cory,
>>
>> Good news.
>>
>> Regarding your second question about PRMSL, it's an easy fix.  In the config file "PointStatConfig_PPmsl", just change
>> vx_grib_code[] = [ "PRMSL/P0"];
>> ... to ...
>> vx_grib_code[] = [ "PRMSL/Z0"];
>>
>> Here's the reasoning -
>> P0 tells Point-Stat to look for observations which have a corresponding pressure level value of 0 (i.e. obs_arr[2] = p_level = 0 in the netCDF observations).  Of course, none of your observations have
>> a pressure level of 0!
>> Z0 tells Point-Stat that we've verifying at a vertical level rather than a pressure level.  When Z is set to 0, 2, or 10 (i.e. surface), Point-Stat will use any observations with a message type of
>> APDSFC or SFCSHP.  Currently, MET really only verifies at pressure levels or at the surface.  I'd be interested to hear if there'd ever be a need to verify at a vertical level other than the surface.
>>
>> So I was able to run your PMSL forecast: nz12kmN_d2_08012112_0006.00000_sslp.grb
>> And compare to the your PMSL observations: nz_metar_08012118_PPmsl.nc
>> Point-Stat found 121 pairs of observations to use.  However, only 63 of those pairs contained valid data for both forecast and observation, so that's while you'll see a count of 63 in the CNT output
>> file from Point-Stat.
>>
>> Regarding your first question, about Spearman's Rank Correlation being negative (around -3.3) I'm going to refer you to Lacey Holland, a scientist in our group.  I don't know much about that
>> statistic, but hopefully Lacey can let me know if there's a problem in the way MET computes it.
>>
>> Hope this helps,
>> John Halley Gotway
>>
>>
>> Cory Davis wrote:
>>> Hi there,
>>> I have a few questions and concerns about MET and in particular the
>>> point_stat tool.  These issues are related to whether I am using 2D
>>> model output fields correctly, negative returned values for the Spearman
>>> rank correlation coefficient, and trouble verifying mean sea level
>>> pressure.
>>>
>>> I have managed to write python code which converts our METAR
>>> observations (already in netcdf) into MET compatible netcdf files.
>>> Also, our operational system already produces grib output via RIP for
>>> several variables, for instance 2m temperature, 10m windspeed, and mean
>>> sea level pressure, and these should correspond directly to the METAR
>>> observations.  I got the impression from the MET documentation that it
>>> is really expecting 3D model fields. However point_stat does run with
>>> these 2D model files, and also produces sensible output, at least for 2m
>>> temperature and 10m wind speed.  However, there does seem to be a
>>> problem with the Spearman rank correlation coefficient.  It is negative.
>>> Given that all the other returned values seem reasonable - the first
>>> impression is that this is a bug or another architecture dependent
>>> problem.  I have attached, obs., model, config, and output that should
>>> reproduce this.
>>>
>>> For the mean sea level pressure I have a different problem: point_stat
>>> detects no pairs and hence no statistics.  I don't know why this should
>>> be the case given that the obs. and model files were produced by the
>>> same process as the T2 and windspeed files.  It is possibly an issue
>>> about how one specifies the level in the PointStatConfig_PPmsl file.
>>> Also, I will have a closer look at the grib file to see if this is
>>> somehow different to the T2 and ws10 grib files.
>>>
>>> Any help with this would be hugely appreciated.
>>>
>>> Cheers,
>>> Cory.
>>>
>>>
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