GPSRO Usage at ECMWF
Deterministic models assimilating RO
- ECMWF IFS – global model:
- T1279 resolution (~16 km)
- 137 vertical levels (lid ~ 80 km)
- Run twice a day
Data assimilation method
- Global model:
- 4D-Var, with 6 hour window (early delivery), and 12 hour window (delayed cutoff).
RO quantity assimilated
- Bending angle
- 2D operator
- Tangent point drift included
- Horizontal thinning to screen duplicate observations. (~100 km and 1hour)
- No bias correction
- A background check is performed in the first trajectory “screening” run
- 4D-Var assimilation, including variational quality control
Observation error characteristics
- Global model, given in impact height, h. 20 % at h=0, falling to 1 % at h=10 km. Above h=10 km max(1%, 3 microradians).
Strong impact on stratospheric temperatures. Ajoint sensitivity for September and October 2011 attached, for 24 hour forecast errors, computed up to 80 km.