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Model Evaluation Tools (MET): An Overview. 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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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
Working Example:6-h precip forecast valid 00z 2 June 08 Forecast Observations
Stage IV Hourly Precip Files • ST4.2008060119.01h • ST4.2008060120.01h • ST4.2008060121.01h • ST4.2008060122.01h • ST4.2008060123.01h • ST4.2008060200.01h
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
PCP-Combine command options pcp_combine init_time in_accum valid_time out_accum out_file [-pcpdir path] [-pcprx reg_exp]
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).
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”
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
Regrid forecasts with “copygb” Output of wgrib –V on Stage IV file yields:polar 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"
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
PCP-Combine for WRF files:Subtract 15-h from 21-h precip • pcp_combine -subtract WRFPRS21.tm00.d01.grb.new 21 WRFPRS15.tm00.d01.grb.new 15 WRFPRS_6hr.nc
MODE command mode fcst_file obs_file Config_file [options] Configuration file: WrfModeConfig mode WRFPRS_6hr.nc obs_6hr.nc WrfModeConfig
MODE output • 3 output formats– ASCII,NetCDF,PS • mode_APCP_06_SFC_vs_APCP_06_SFC_240000L_20080602_030000V_060000A_cts.txt • mode_APCP_06_SFC_vs_APCP_06_SFC_240000L_20080602_030000V_060000A_obj.nc • mode_APCP_06_SFC_vs_APCP_06_SFC_240000L_20080602_030000V_060000A_obj.txt • mode_APCP_06_SFC_vs_APCP_06_SFC_240000L_20080602_030000V_060000A.ps
