Cycle 41r1 summary of changes

IFS cycle 41r1 includes a large number of changes affecting all components of the forecasting system. Significant changes to the model physics, assimilation, observation usage and the ensemble configuration have shown to deliver significant analysis and forecast benefit.

The domain of the high-resolution limited-area wave model is extended to the entire globe, and hence is no longer 'limited-area'.

The first operational run using IFS cycle 41r1 was the 12 UTC analysis and forecast on 12 May 2015. The monthly forecast extension to the ensemble was run with the new IFS cycle for the first time the following Thursday, 14 May 2015.

Implementation date 12 May 2015  See News article
IFS Documentation CY41R1  
Detailed description of changes  
Key characteristics of our current forecasting system  

Horizontal (unchanged)

  • Atmospheric
    • HRES: T1279
    • ENS: Leg A T639, Leg B T319, Leg C T255
  • Wave
    • HRES: 0.25 degrees
    • ENS: 0.5 degrees


Vertical (unchanged)

  • Atmospheric
    • HRES: L137
    • ENS: L91



Data set affected

  • HRES
  • ENS
Scorecard for 41r1  
Meteorological changes
  • New surface climate fields (land-sea mask, sub-grid orography), also affecting number of land and sea points.
  • New CO2/O3/CH4 climatologies from latest MACC-II reanalysis produced at ECMWF.
  • Revised semi-Lagrangian extrapolation reducing stratospheric noise.
  • Revised interpolation of moist variables in the upper-troposphere/lower stratosphere (UTLS).
  • Cloud scheme change of rain evaporation, auto-conversion/accretion, riming, precipitation fraction.
  • Improved representation of supercooled "freezing" rain.
  • Modified convective detrainment.
  • Activation of the lake model (FLAKE).
  • Active use of wave modified stress in coupled mode.
  • Revised sea-ice minimum threshold, sea-ice roughness length and consistency between SST and sea ice concentration. 
Data assimilation
  • Upgrade of inner loop resolutions of 4D-Var to TL255 for each of the three iterations of the outer loops.
  • Reduction of number of iterations in 1st inner loop and use of full linear physics package.
  • Changed calculation of background error covariances from using EDA samples of perturbations from last cycle (1/3) and climatology (2/3).
  • Active use of:
    • SSMIS moisture sounding channels over land and sea-ice;
    • surface-sensitive ATMS channels over land;
    • ASCAT in soil moisture analysis;
    • Altika and Cryosat altimeter wave height data.
  • Upgrade of radiance observation operator with RTTOV-11.
  • Assimilation of GPS-RO with two-dimensional observation operator.
  • Assimilation of high-resolution radiosondes.

Medium-range/monthly ensemble (ENS)

  • LegB extended to 46 days (instead of 32) on Mondays and Thursday (at 00UTC).
  • Twice weekly 11-member re-forecasts.
Meteorological impacts
  • Upper Air
  • Weather parameters
  • Wave forecast
  • Synoptic evaluation
  • Monthly forecast
Technical changes
  • New land-sea mask, orography and climate fields.
  • ENS Leg B extended from 32 to 46 days on Mondays and Thursday (at 00UTC).
  • New ENS re-forecast configuration
  • Increase frequency of steps for Surface thermal radiation downwards (STRD, paramId=175) in the Monthly Forecast and re-forecasts.
  • Changes in the Extreme Forecast Index (EFI) and Shift of Tails (SOT).
  • Changes to the fields CIN and CBH to include a bitmap with missing values.
  • The domain of limited-area ocean wave model is extended to the full globe.
Model ID
  • Atmospheric: 145
  • Ocean wave: 111
  • Limited-area ocean wave: 211
New disseminated model output

IFS cycle 41r1 introduced a large number of new disseminated model output. These include:

  • Parameters from the lake model;
  • Precipitation type and precipitation rate parameters;
  • Parameters associated with the new partitioning of ocean waves into wind waves and swell.

For a full list, see the table in the Detailed description of changes.

In addition, ENS model level parameters are made available in dissemination for all members at all post-processing time steps to day 15.  These fields are not archived in MARS.


Discontinued disseminated model output

After consultation with our users, we have stopped archiving the Budget Values (shortName BV, paramId 128128).

In addition, the surface roughness fields SR (paramId 173128) and LSRH (paramId 234128) are obsolete and should no longer be used. Archiving of these parameters will be discontinued in a later cycle.

e-suite experiment number 0067