Transcript Model Evaluation Tools (MET): An Overview

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
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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
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–
–
–
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_240
000L_20080602_030000V_060000A_cts.txt
• mode_APCP_06_SFC_vs_APCP_06_SFC_240
000L_20080602_030000V_060000A_obj.nc
• mode_APCP_06_SFC_vs_APCP_06_SFC_240
000L_20080602_030000V_060000A_obj.txt
• mode_APCP_06_SFC_vs_APCP_06_SFC_240
000L_20080602_030000V_060000A.ps
No Mask
Masking Obs
0.1 mm thresh
5.0 mm thresh
Centroid radius variations
800/(delta-x)
200/(delta-x)