[Met_help] PWAT verification with MET Tools

[John Halley Gotway]

Thomas,

I'm thinking that you've made a mistake in how you're calling Point-Stat on the command line.

Take a look at how you're calling it on the command line and make sure it matches the calling sequence:
point_stat fcst_file obs_file config_file

Based on the error, my guess is that you're passing the "obs_file" in the "config_file" spot.

John

Thomas Schwitalla wrote:
> John,
> 
> with
> 
> fcst_field[] = [ "PWAT/L0" ];
> 
> it works.
> Concerning the times, I had a mistake in my original conversion program
> which should be solved now....
> 
> but now I get:
> 
> config() -> syntax error in file "20070720_pwat.nc"
> 
>      line   = 1
> 
>      econfig_column = 7
> 
>      text   = "V8"
> 
> CDF
> 
> 
> Thanks again for your help!
> 
> Thomas
> 
> 
> John Halley Gotway schrieb:
>> Thomas,
>>
>> OK, sorry, my mistake.  You need to use:
>> fcst_field[] = [ "PWAT/L0" ];
>>
>> The "L0" says "give me a field with a level value of 0 and I don't
>> care what type of level it is".  When you say "Z0" the code looks at
>> what type of level is in the GRIB file and only uses the one
>> defined on vertical levels.  But PWAT isn't defined on a vertical
>> level - it's level type is the "entire atmosphere (considered as a
>> single layer)".
>>
>> The reason why we have all these silly letters is to avoid conflicts. 
>> For example, other users have had temperature at 2-meters and 2 mb. 
>> Both records will have a level value of 2, but "Z2" will get
>> you the first one, while "P2" will get you the second one.  And if all
>> else fails, you can always say "PWAT/R171" to explicitly give you GRIB
>> record number 171 - which wgrib told us is the record
>> number for PWAT in that file.
>>
>> I was able to get it to run using "PWAT/L0", but initially Point-Stat
>> found no matched pairs.  It looks like there a slight time offset
>> that's causing the problem.  This is a 1-hour forecast
>> initialized at 2007072000 - so the valid time is 2007072001.  I looked
>> at the observations your using, and they range in time from
>> 20070720_230700 to 20070720_235200.
>>
>> You're welcome to compare this forecast to these observations if you'd
>> like, but you'll need to set the matching time window differently to
>> do so.  In the config file, you can set the "beg_ds" and
>> "end_ds" parameters to define the matching time window in reference to
>> the forecast time window.  Alternatively, the "-valid_beg" and
>> "-valid_end" command line options override the "beg_ds" and
>> "end_ds" settings in the config file.
>>
>> Once I changed the time window, I was able to get matched pairs.
>>
>> Hope that helps.
>>
>> John
>>
>> Thomas Schwitalla wrote:
>>  
>>> I uploaded the data on your ftp server, as one timestep is about
>>> 100MB...
>>>
>>> Thanks again for your effort! Your reaction time is fantastic! 8-)
>>>
>>> Thomas
>>>
>>> John Halley Gotway schrieb:
>>>    
>>>> Thomas,
>>>>
>>>> Please send me a sample forecast file, a sample ASCII file, and the
>>>> PointStatConfig file you're using.  I'll take a look and see if I can
>>>> figure it out.
>>>>
>>>> If the forecast file is pretty large, you could post those to our
>>>> anonymous ftp site:
>>>>
>>>> ftp ftp.rap.ucar.edu
>>>> username=anonymous
>>>> password="your email address"
>>>> cd incoming/irap/met_help/schwitalla_data
>>>> put "your files, 1 at a time"
>>>> bye
>>>>
>>>> Just let me know when you've posted the files.
>>>>
>>>> Thanks,
>>>> John
>>>>
>>>> Thomas Schwitalla wrote:
>>>>  
>>>>      
>>>>> John,
>>>>>
>>>>> when I try your suggestion, I got the following message:
>>>>>
>>>>> ERROR: process_grib_codes() -> no records matching GRIB code 54 with
>>>>> level indicator of Z0 found in GRIB file:
>>>>> /taifun/20070720_cops_WRF_sensitivity/assim/wrf_files/postprd/WRFPRS_2007072000_d01.002
>>>>>
>>>>>
>>>>>
>>>>>
>>>>> "wgrib -v" on this file gives:
>>>>>
>>>>> 171:80565400:D=2007072001:PWAT:atmos col:kpds=54,200,0:1hr
>>>>> fcst:winds in
>>>>> grid direction:"Precipitable water [kg/m^2]
>>>>>
>>>>> A sample line of my ASCII file reads:
>>>>>
>>>>> ADPSFC  0007  20070720_233700     52.9480     12.3922     60.9550  54
>>>>> -9999     60.9550     31.3000
>>>>>
>>>>> Now I am a bit confused...
>>>>>
>>>>> Thomas
>>>>>
>>>>> John Halley Gotway schrieb:
>>>>>           
>>>>>> Thomas,
>>>>>>
>>>>>> Just to be clear...
>>>>>> (1) Your forecast from WPP of precipitable water is a value that's
>>>>>> integrated over the whole column of air above each grid point.
>>>>>> (2) Your point observations of precipitable water are the same - a
>>>>>> value for the whole column of air above the observation point at the
>>>>>> surface.
>>>>>>
>>>>>> If that's true, I'd set up the PointStatConfig file as follows:
>>>>>> fcst_field[] = [ "PWAT/Z0" ];
>>>>>> message_type[] = [ "ADPSFC" ];
>>>>>>
>>>>>> That means "give me the precipitable water field with a level
>>>>>> value of
>>>>>> 0", which is how's it's stored in your GRIB file.  And verify against
>>>>>> "surface" observations.  When you call ASCII2NC, be sure to
>>>>>> encode these PWAT observations using the "ADPSFC" message type.
>>>>>>
>>>>>> Give that a try and let me know if you have any problems.
>>>>>>
>>>>>> Thanks,
>>>>>> John
>>>>>>
>>>>>> Thomas Schwitalla wrote:
>>>>>>  
>>>>>>               
>>>>>>> John,
>>>>>>>
>>>>>>> I want to verify WRF forecasts (postprocessed with WPP)  with PWAT
>>>>>>> data
>>>>>>> from GPS stations. I already wrote it to NETCDF with ascii2nc but I
>>>>>>> haven't figured out how to edit PointStatConfig that I can use
>>>>>>> PWAT. My
>>>>>>> problem is: What value to set for the level type/code as PWAT is an
>>>>>>> integrated value?
>>>>>>>
>>>>>>> wgrib output looks as follows:
>>>>>>>
>>>>>>> PWAT kpds5=54 kpds6=200 kpds7=0 levels=(0,0) grid=255 atmos col 1hr
>>>>>>> fcst:
>>>>>>>
>>>>>>>
>>>>>>> Best regards,
>>>>>>> Thomas
>>>>>>>
>>>>>>>                         
>>>>>             
>>>     
> 
>