Use of AMVs in the NCEP model

Physical characteristics

• FV3GFS model, non-hydrostatic, C768 (~13km deterministic) GFS Physics, GFDL Microphysics, FV3GDAS C384 (25km, 80 member ensemble)
• Horizontal resolution: C768 with gaussian grid 1760×880
• Vertical resolution: 127 vertical layers with hybrid configuration from sigma level to isobaric pressure level, top at 0.2 hPa
• For more info on the FV3 dynamic code: https://www.gfdl.noaa.gov/fv3/

Data assimilation method

• Type: Hybrid 4DEnVar
• Time window: T ± 3 hr, analysis times (T): 00, 06, 12, 18 Z
• Time constraints (model runtime):
• Main forecast run: 14 min before time window ends
• Update run: 3 hr 50 min after time window ends
• EnKF for ensemble perturbations

AMV types assimilated

Global Model

• Meteosat-10 IR, VIS, cloudy WV
• Meteosat-9 IR, VIS, cloudy WV
• GOES-18 IR, cloudy WV, clear air WA
• GOES-16 IR, cloudy WV, clear air WA
• HIMAWARI-9 IR, VIS, cloudy WV
• NESDIS Terra IR, cloudy WV, clear sky WV
• NESDIS Aqua IR, cloudy WV, clear sky WV
• NESDIS S-NPP and JPSS/NOAA-20 VIIRS IR
• NESDIS Metop-B and Metop-C AVHRR IR
• NOAA-15/18/19 IR
• LEOGEO IR

Quality control

Blacklisting in space

• Zenith angle greater than 68 for satellite winds from geostationary satellites
• Pressure level less than 125 hPa, or greater than 950 hPa
• No visible data used if pressure level less than 700 hPa
• Pressure level is 50 hPa above tropopause
• NESDIDS IR and EUMETSAT IR between 800-400 hPa
• JMA IR between 800-500 hPa removed
• 600-250 hPa for MODIS water vapor deep layer wind
• Pressure below 600 hPa for MODIS water vapor cloud top wind
• Height above 250 hPa for MODIS IR wind
• IR winds over land

QI thresholds

QI without forecast guess less than 85 for JMA and EUMETSAT winds, and less than 90 for NESDIS winds

Thinning

• 200(km)x200(km)x100mb box is used to thin Met-9, Met-10, Him-9 winds

Background check

• Gross check: C=vector difference (O-B)/observation error, data rejected if C > gross check limit
• Asymmetric gross check: data rejected if O-B speed < 0 and C > f * gross check limit
• For GOES IR and water vapor cloud top winds, asymmetric gross check applies between 300-400 hPa
• FOR EUMESAT IR winds, asymmetric gross check applies between 200-400 hPa
• For MODIS winds asymmetric gross check applies all levels
• Log-Normal Vector Difference check applied to Polar and GOES WVCA winds: C=vector difference (O-B)/log(obs speed), data rejected of C > = 3
• LNVD check also rejects winds over a non-ocean surface within 110 hPa (for GOES) or 200 hPa (Polar) of the surface

Observation errors