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

QC

  • 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).

Impact

Strong impact on stratospheric temperatures. Ajoint sensitivity for September and October 2011 attached, for 24 hour forecast errors, computed up to 80 km.

ODRD_DEC_forSean