Model Evaluation Tools MET An Overview MET Verification

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 00 z 2 June 08 Forecast Observations

Stage IV Hourly Precip Files • • • ST 4. 2008060119. 01 h ST 4. 2008060120. 01 h ST 4. 2008060121. 01 h ST 4. 2008060122. 01 h ST 4. 2008060123. 01 h ST 4. 2008060200. 01 h

4 -km Stage IV grid Specification 1121 x 881 polar stereographic grid. LL point: 23. 117 N 119. 023 W. UL point: 53. 509 N 134. 039 W. LR point: 19. 805 N 80. 750 W. UR point: 45. 619 N 59. 959 W. True longitude: 105 W. The resolution is 4. 7625 km at 60 N. 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/on 388/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 Net. CDF file in HH format (required). • out_file: – Name of the output Net. CDF 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 0000_000000 01 20080602_000000 6 obs_6 hr. nc -pcpdir. – Note: Set init_time to 0000_000000 when summing observation files • Above command yields 6 -hour OBS precip valid at 00 z 2 June 2008 in netcdf format – Filename “obs_6 hr. nc”

Regrid forecasts with “copygb” • STIV Obs Grid – 1121 x 881, 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 1 23. 117000 Long 1 -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 0 64"

WRF Forecast GRIB files: 03 z 1 June initialization time • copygb -xg "$grid" -i 1 -X WRFPRS 15. tm 00. d 01. grb. new • copygb -xg "$grid" -i 1 -X WRFPRS 21. tm 00. d 01. grb. new

PCP-Combine for WRF files: Subtract 15 -h from 21 -h precip • pcp_combine -subtract WRFPRS 21. tm 00. d 01. grb. new 21 WRFPRS 15. tm 00. d 01. grb. new 15 WRFPRS_6 hr. nc

MODE command mode fcst_file obs_file Config_file [options] Configuration file: Wrf. Mode. Config mode WRFPRS_6 hr. nc obs_6 hr. nc Wrf. Mode. Config

MODE output • 3 output formats– ASCII, Net. CDF, PS • mode_APCP_06_SFC_vs_APCP_06_SFC_240 000 L_20080602_030000 V_060000 A_cts. txt • mode_APCP_06_SFC_vs_APCP_06_SFC_240 000 L_20080602_030000 V_060000 A_obj. nc • mode_APCP_06_SFC_vs_APCP_06_SFC_240 000 L_20080602_030000 V_060000 A_obj. txt • mode_APCP_06_SFC_vs_APCP_06_SFC_240 000 L_20080602_030000 V_060000 A. ps

No Masking Obs

0. 1 mm thresh 5. 0 mm thresh

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