Cycle 31r1 summary of changes

Implementation date

12 September 2006

IFS Documentation CY31R1  
Key characteristics of our forecasting system  

Horizontal  (unchanged)

  • Atmospheric
    • HRES: TL799
    • ENS: Leg A TL399
  • Wave
    • HRES: 0.36 degrees
    • ENS: 0.5 degrees
    • LAW: 0.1 degrees

Vertical (unchanged)

  • Atmospheric
    • HRES: L91
    • ENS: L62
Data set affected
  • HRES
  • ENS
Scorecard -
Meteorological changes
  • Revisions to the cloud scheme, including treatment of ice supersaturation and new numerics
  • Implicit computation of convective transports
  • Introduction of turbulent orographic form drag scheme and revision to sub-grid scale orographic drag scheme
  • Gust fix for orography and stochastic physics
  • Reduction of ocean surface relative humidity from 100% to 98% (due to salinity effects)
  • Revised assimilation of rain-affected radiances
  • Variational bias correction of satellite radiances
  • Thinning of low level AMDAR data (mainly affects Japanese AMDAR network)
Meteorological impacts
  • statistically significant positive impact in the free atmosphere in the northern hemisphere up to day 7, with generally neutral to positive impacts elsewhere
  • improvement of forecast precipitations over Europe
  • Increases in atmospheric humidity have led to reduced low temperature biases in the upper troposphere ( 300hPa), but increased cold biases in the lower stratosphere.
Technical changes
  • Computation of EPS ensemble mean and standard deviation fields was revised
  • Computation of accumulated fields in VarEPS is available in pdf format Computation of accumulated_fields in VarEPS
  • GRIB headers of ENS fields use definition 27 (archive only) to contain the VarEPS leg information in the local extension.
  • Forecast step 0 will be archived and offered in dissemination for STREAM= SCDA runs at 06 and 18 UTC. This is to harmonise the runs from the DA and DCDA streams.
  • 3-hourly postprocessing for the main deterministic forecast runs (STREAM=DA) will be extended from 96 to 144 hours. The extra data will be available through MARS and dissemination.
  • The EPS ensemble mean and standard deviation fields for the parameters geopotential height at 1000 and 500hPa and temperature at 850 and 500hPa will now be computed on the model grid, which will be the archive grid representation and also be made available for dissemination.
Model ID
  • Atmospheric: 128
  • Ocean wave: 116
  • Limited-area ocean wave: 216
New disseminated model output Additional post-processing steps  in the deterministic T799 forecast
Discontinued disseminated model output -  
e-suite experiment number 0031