[Met_help] point_stat config question

[John Halley Gotway]

Ruifang,

The behavior you're seeing is correct.  The MPR output would be the same.  However, the values in the contingency tables (CTC line type, for example) should be different when choosing different
thresholds.

Here's what's going on...  When you run Point-Stat, you can think of it as setting up a bucket for each combination of forecast field/masking region/interpolation method.  So for example, suppose you
configure Point-Stat to verify 2-meter temperature and 500mb temperature over 3 masking regions, your FULL domain and then two subdomains.  And you're using the nearest neighbor interpolation method.
 In this case, we'd be verifying 2 fields over 3 regions using 1 interpolation method.  So Point-Stat will set up 6 "buckets", 3 for 2-meter temp and 3 for 500mb temp.

Next, Point-Stat looks at each one of the point observation values you've passed to it.  If the observation type (i.e. 2-m temp) matches the forecast type, and it's in the correct masking region,
it'll interpolate the forecast values to the observation location to create a matched pair.  Then it throws that matched fcst-obs pair into the appropriate bucket.  Point-Stat processes through all of
the point observations in this way, computing matched pairs, and throwing them in the right buckets.

After that's finished, it'll compute whatever statistics you've requested using whatever threshold values you've set.  For example, if you set threshold values of ">273.0" and ">283.0" for 2-m temp,
it'll apply those to all of the matched pairs in the "bucket" and compute contingency tables and stats.  However, the choice of threshold has no effect on which matched pairs make it into the bucket
to begin with.

The matched pair (MPR) output consists of all the matched pairs that are in the buckets.  So the MPR output does NOT depend on any choice of threshold value.

Does that make sense?

Thanks,
John

Ruifang Li wrote:
> Hi John,
> I run point_stat tool and did two test with different fcst_thresh[] in
> config file. I expect the different MPR output, but they create same MPR. I
> could not figure out why. In my understanding, if fcst_thresh eq 0, fcst
> value in MPR should be 0. if  fcst_thresh le 100 fcst value in MPR should be
> le 100, right?
> 
> Here are two fcst_thresh:
> 
> fcst_field[] =
> ["UGRD/Z10","UGRD/P1000","UGRD/P925","UGRD/P850","UGRD/P700","UGRD/P500","UGRD/P400","UGRD/P300","UGRD/P250","UGRD/P200","UGRD/P150","UGRD/P100","UGRD/P70","UGRD/P50","UGRD/P30","UGRD/P20","UGRD/P10"
> ];
> 
> //fcst_thresh[] = [ "le100",
> "le10","le10","le100","le100","le100","le100","le100","le100","le100","le100","le100",
> "le100","le100", "le100","le100","le100" ];
> fcst_thresh[] = [ "eq0",
> "eq0","eq0","eq0","eq0","eq0","eq0","le10","eq0","eq0","eq0","eq0",
> "eq0","eq0", "eq0","eq0","eq0" ];
> 
> Here is MPR file:
> 
> /ptmp/lir/test/2009_t8_15km/verify_met2.0/test% ls -l
> /ptmp/lir/data/2009_t8_15km/verify_met/gsi/point_stat/UGRD/2007081512/
> total 14208
> -rw-r--r--    1 lir      ncar         786984 Aug 20 16:05
> point_stat_000000L_20070815_120000V.stat
> -rw-r--r--    1 lir      ncar         652568 Aug 20 16:05
> point_stat_000000L_20070815_120000V_mpr.txt
> -rw-r--r--    1 lir      ncar         698412 Aug 20 16:05
> point_stat_120000L_20070816_000000V.stat
> -rw-r--r--    1 lir      ncar         579124 Aug 20 16:05
> point_stat_120000L_20070816_000000V_mpr.txt
> -rw-r--r--    1 lir      ncar         761574 Aug 20 16:05
> point_stat_240000L_20070816_120000V.stat
> -rw-r--r--    1 lir      ncar         631498 Aug 20 16:05
> point_stat_240000L_20070816_120000V_mpr.txt
> -rw-r--r--    1 lir      ncar         740520 Aug 20 16:05
> point_stat_360000L_20070817_000000V.stat
> -rw-r--r--    1 lir      ncar         614040 Aug 20 16:05
> point_stat_360000L_20070817_000000V_mpr.txt
> -rw-r--r--    1 lir      ncar         791340 Aug 20 16:05
> point_stat_480000L_20070817_120000V.stat
> -rw-r--r--    1 lir      ncar         656180 Aug 20 16:05
> point_stat_480000L_20070817_120000V_mpr.txt
> 
> Script:
> /ptmp/lir/test/2009_t8_15km/verify_met2.0/test% point_stat_gsi.ksh
> *** Running POINT_STAT on WRF OUTPUT ***
> ***          UGRD                ***
> GSL_RNG_TYPE=mt19937
> GSL_RNG_SEED=2412285258
> Forecast File:
> /ptmp/lir/data/2009_t8_15km/verify_met2.0/gsi/wpp/2007081512/postprd/wrfprs_d01.000
> Climatology File: none
> Configuration File: ./config/PointStatConfig_GSI.UGRD
> Observation File:
> /ptmp/lir/data/2009_t8_15km/verify_met2.0/ob_nc/2007081512/ob.nc.qc2
> 
> ----------------------------------------
> 
> Reading records for UGRD/Z10.
> For UGRD/Z10 found 1 forecast levels and 0 climatology levels.
> 
> 
> Thanks for your support,
> 
> 
> ------------------------------------------------------------------------
> 
> _______________________________________________
> Met_help mailing list
> Met_help at mailman.ucar.edu
> http://mailman.ucar.edu/mailman/listinfo/met_help