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

Working Example: 6-h precip forecast valid 00z 2 June 08 Forecast Observations

Stage IV Hourly Precip Files ST h ST h ST h ST h ST h ST h

4-km Stage IV grid Specification 1121 x 881 polar stereographic grid. LL point: N W. UL point: N W. LR point: N W. UR point: N W. True longitude: 105W. The resolution is km at 60N. The pole point is (I,J) = (400.5,1600.5) This and numerous other standard grids defined at:

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 _ _ obs_6hr.nc -pcpdir. –Note: Set init_time to _ 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: Lat Long Orient , north pole (1121 x 881) Dx 4763 Dy 4763 scan 64 mode 8 set grid=" "

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_ L_ _030000V_060000A_cts.txt mode_APCP_06_SFC_vs_APCP_06_SFC_ L_ _030000V_060000A_obj.nc mode_APCP_06_SFC_vs_APCP_06_SFC_ L_ _030000V_060000A_obj.txt mode_APCP_06_SFC_vs_APCP_06_SFC_ L_ _030000V_060000A.ps

No Mask Masking Obs

0.1 mm thresh 5.0 mm thresh

Centroid radius variations 800/(delta-x) 200/(delta-x)