AMV usage in the Env. Canada NWP model

Use of AMVs in the Environment Canada model

Physical characteristics

Global Model

  • Grid-point model 2x1287x417 Yin-Yang horizontal grid
  • Horizontal resolution: ~25 km
  • Vertical resolution: 80 levels, model top 0.1 hPa

Data assimilation method

Global Model

  • 4D-EnVar, 6-h assimilation window, 4DIAU, 0.33° x 0.33° increment resolution
  • Time window: T ± 3 hr, analysis times (T): 00, 06, 12, 18 Z
  • Time constraints (model runtime):
  • Early analysis and forecast run: T+3 hr, forecast at 00 and 12Z only
  • Update analysis run: ~T+9 hr at 00 and 12Z, T+6 hr at 06 and 18Z
    25 time bins in the 6-h assimilation window.

AMV types assimilated

Global Model

  • Meteosat-11 IR, VIS, WV
  • Meteosat-8 IR, VIS, WV
  • GOES-15 IR 3.9 IR 10.7, VIS, WV
  • NESDIS MODIS Terra IR, WV
  • NESDIS MODIS Aqua IR, WV
  • direct broadcast MODIS from Tromso, Fairbanks and McMurdo
  • AVHRR NOAA-15/18/19 IR
  • EUMETSAT Single Metop-A/B IR
  • EUMETSAT Dual-Metop IR
  • NPP IR
  • Himawari-8/9 IR, VIS, WV 6.9

Global quality control

Blacklisting in space

  • All geostationary winds beyond 68° satellite zenith angle
  • All winds above 200 hPa (160 hPa over the Tropics)
  • All winds below 1000 hPa (400 hPa over land)
  • All VIS winds above 700 hPa
  • All geostationary WV winds below 400 hPa
  • All Meteosat-11, Meteosat-8 and Himawari-8/9 winds over land north of 25N, south of 20S and below 400 hPa
  • All GOES winds over land north of 20N, south of 20S and below 400 hPa
  • All polar WV winds below 550 hPa
  • All polar IR winds below 700 hPa
  • All polar winds over land below 400 hPa
  • All Dual Metop outside the latitude bands 40-60 N/S
  • All wind speeds below 2.5 m/s

QI thresholds

Note: There are no QI thresholds applied to the polar winds except EUMETSAT Single Metop and Dual Metop (QI1>80)

  extratropics tropics
HL ML LL HL ML LL
GOES-15 QI1 IR 85 80 80 90 90 90
WV 80 90
Meteosat-8/-11 QI1 IR 85 80 80 90 90 90
VIS 65 90
WV 80 90
Himawari-8 QI1 ALL 85 85 85 85 85 85

tropics: 20S-20N
extratropics: polewards of 20S/N

hl: 10-400 hPa
ml: 400-700 hPa
ll: 700-1000 hPa

QI1 – EUMETSAT QI with first guess check
QI2 – EUMETSAT QI without first guess check
RFF – Recursive Filter Function (CIMSS/NESDIS)

For information on how the quality indicators are formulated see Holmlund (1998, Weather Forecasting 13 1093-1104) and Hayden and Purser (1995, Journal of Applied Meteorology 34 3-15).

Thinning

  • The AMV are first sorted according to their quality index (QI1) from highest to lowest on 10 layers.
  • For each satellite, the selection process starts from the AMV with the highest QI1.
  • The next AMV is selected if all previous selected data in the same layer and within 6 time bins (1h30) are beyond 200 km.
  • The selection process is repeated for all subsequent AMVs.

Background check

The background check is applied to the vector difference between the AMV and the corresponding background value. A variational quality control is then applied on each wind component during the minimization.

Observation errors

Similar to Met Office – observation errors calculated individually for each wind using estimates of the error in vector, error in height and variation in the background wind column.