Use of AMVs in the Environment Canada model
Contents
Physical characteristics
Global Model
- Grid-point model 2x2047x683 Yin-Yang horizontal grid
- Horizontal resolution: ~15 km
- Vertical resolution: 84 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 UTC
- Time constraints (model runtime):
- Early analysis and forecast run: T+3 hr, forecast at 00 and 12 UTC only
- Update analysis run: ~T+7 hr at 00, 06, 12 and 18 UTC
25 time bins in the 6-h assimilation window.
AMV types assimilated
Global Model
- Meteosat-10 IR, VIS, WV
- Meteosat-9 IR, VIS, WV
- GOES-16 IR, VIS, WV 6.2
- GOES-18 IR, VIS, WV 6.2
- 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-B/C IR
- EUMETSAT Dual-Metop IR
- VIIRS NPP IR
- VIIRS NOAA-20 IR
- Himawari-9/8 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 3.0 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 | |||
| Meteosat-8/-11 | QI1 | IR | 85 | 80 | 80 | 90 | 90 | 90 |
| VIS | – | – | 65 | – | – | 90 | ||
| WV | 80 | – | – | 90 | – | – | ||
| GOES-16/17 | QI2 | IR | 96 | 96 | 95 | 96 | 98 | 95 |
| VIS | – | – | 95 | – | – | 95 | ||
| 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 (QI1/2) from highest to lowest on 10 layers.
- For each satellite, the selection process starts from the AMV with the highest QI1/2.
- 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.
- Therefore, a minimal distance of 200km and a minimal time difference of 1h30 between adjacent AMVs are strictly imposed at each levels
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