Model Evaluation Tools (MET): An Overview

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Model Evaluation Tools(MET) An Overview
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MET Verification Techniques

• Standard verification methods
• gridded model data to point-based observations
• gridded model data to gridded observations
• Object-based verification method
• comparing gridded model data to gridded
  observations

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Working Example6-h precip forecast valid 00z 2
June 08
Forecast
Observations
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Stage IV Hourly Precip Files

• ST4.2008060119.01h
• ST4.2008060120.01h
• ST4.2008060121.01h
• ST4.2008060122.01h
• ST4.2008060123.01h
• ST4.2008060200.01h

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4-km Stage IV grid Specification 1121 x 881
polar stereographic grid. LL point 23.117N
119.023W. UL point 53.509N 134.039W. LR point
19.805N 80.750W. UR point 45.619N 59.959W.
True longitude 105W. The resolution is
4.7625km at 60N. The pole point is (I,J)
(400.5,1600.5) This and numerous other standard
grids defined at http//www.nco.ncep.noaa.gov/pmb
/docs/on388/tableb.html
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PCP-Combine command options

• pcp_combine init_time
• in_accum
• valid_time
• out_accum
• out_file
• -pcpdir path
• -pcprx reg_exp

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PCP-combine command options

• init_time
• Initialization time of the input Grib files in
  YYYYMMDD_HHMMSS format (required).
• in_accum
• Accumulation interval of the input Grib files in
  HH format (required).
• valid_time
• Desired valid time in YYYYMMDD_HHMMSS format
  (required).
• out_accum
• Desired accumulation interval for the output
  NetCDF file in HH format (required).
• out_file
• Name of the output NetCDF file to be written
  consisting of the sum of the accumulation
  intervals (required).

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PCP_combine example Summing individual Stage IV
hourly precip

• pcp_combine -sum 00000000_000000 01
  20080602_000000 6 obs_6hr.nc -pcpdir .
• Note Set init_time to 00000000_000000 when
  summing observation files
• Above command yields 6-hour OBS precip valid at
  00z 2 June 2008 in netcdf format
• Filename obs_6hr.nc

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Regrid forecasts with copygb

• STIV Obs Grid 1121x881,polar stereo,Dx,Dy 4763
• WRF Data Grid
• 308 x 310 Lambert Proj with Dx,Dy 4000
• Extract precip grid from WRF output GRIB file
• Needs to be projected onto OBS grid (i.e. Stage
  IV)
• wgrib V filename provides necessary details on
  each grid

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Regrid forecasts with copygb

• Output of wgrib V on Stage IV file yieldspolar
  stereo Lat1 23.117000 Long1 -119.023000 Orient
  -105.000000, north pole (1121 x 881) Dx 4763
  Dy 4763 scan 64 mode 8
• set grid"255 5 1121 881 23117 -119023 8 -105000
  4763 4763 0 64"

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WRF Forecast GRIB files 03z 1 June
initialization time

• copygb -xg "grid" -i1 -X WRFPRS15.tm00.d01.grb
  WRFPRS15.tm00.d01.grb.new
• copygb -xg "grid" -i1 -X WRFPRS21.tm00.d01.grb
  WRFPRS21.tm00.d01.grb.new

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PCP-Combine for WRF filesSubtract 15-h from
21-h precip

• pcp_combine -subtract WRFPRS21.tm00.d01.grb.new
  21 WRFPRS15.tm00.d01.grb.new 15 WRFPRS_6hr.nc

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MODE command

• mode fcst_file obs_file Config_file options
• Configuration file WrfModeConfig
• mode WRFPRS_6hr.nc obs_6hr.nc WrfModeConfig

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MODE output

• 3 output formats ASCII,NetCDF,PS
• mode_APCP_06_SFC_vs_APCP_06_SFC_240000L_20080602_0
  30000V_060000A_cts.txt
• mode_APCP_06_SFC_vs_APCP_06_SFC_240000L_20080602_0
  30000V_060000A_obj.nc
• mode_APCP_06_SFC_vs_APCP_06_SFC_240000L_20080602_0
  30000V_060000A_obj.txt
• mode_APCP_06_SFC_vs_APCP_06_SFC_240000L_20080602_0
  30000V_060000A.ps

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No Mask Masking Obs
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0.1 mm thresh 5.0 mm thresh
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Centroid radius variations800/(delta-x)
200/(delta-x)