You are viewing an old version of this page. View the current version.

Compare with Current View Page History

« Previous Version 4 Current »

Model configurations

The IFS models the dynamics of the atmosphere and the physical processes that occur, and also other processes that influence the weather e.g. atmospheric composition, surface energy fluxes, the marine environment and processes at the atmosphere/surface interface (scroll down to soil/surface section).  Several configurations of the atmospheric model are used, each tailored towards a specific aim:

There are some slight differences, but generally the same model structure is used in each of the different model configurations.  The relative skill of the models and their strengths have been investigated.

Upgrades in latest cycle of Integrated Forecast System (IFS) model Cy50r1. 

Some major model changes and additions were made to the IFS with the introduction of Cy50r1 in May 2026.  These are:

Observations

  • Upper air observations

    • Temperature and specific humidity increments above the tropopause are constrained by high quality radiosondes.
    • Observation timeslots reduced from 30 minutes to 15 minutes.  This allows a more accurate comparison between the model and the observations.  
    • Wind tracing with-ozone sensitive data.

  • Ocean observations

    • Temperature/salinity profiles (e.g. ARGO, moored buoy, ship subsurface, mammals, gliders, AXBTs etc).
    • Sea Level Anomaly (SLA).

Model

  • Ocean and sea-ice:

    • New ocean and sea ice model based on NEMO-SI3.  Updates include:
      • Improved physical parametrisation.
      • Multi-category sea-ice model with prognostic salinity and melt pond dynamics is introduced.
      • The more advanced SI3 replaces LIM2 for forecasting sea-ice.
      • Albedo diagnosed by sea ice model SI3 replaces climatological sea-ice albedo.
      • Climatological sea-ice albedo replaces with albedo diagnosed by sea-ice model SI3.
      • Generic Length Scale (GLS) turbulence scheme is introduced for better vertical mixing processes.
      • The extended ORCA grid is extended further towards South Pole.
      • New ice parametrisation scheme is included in NEMO.  Snow (single layer representation) on sea-ice tile.  This gives more realistic representation of sea-ice and snowpack properties. 
      • New ensemble analysis system for ocean and sea-ice based on ORAS6 reanalysis.  This is used for initialising both the forecasts and the re-forecasts.
    • Updates include:
      • Hourly surface forcing from ERA5 atmosphere.  This allows much more accurate representation of short-term variability such as diurnal cycle of sea surface temperature.  This was not captured with daily forcing used in earlier systems.
      • Variational assimilation of sea surface temperature (SST) with flow-dependent errors.

  • Wave model:  

    • Refined wave-sea ice coupling with new waves and sea ice interaction.
    • Revised wave model bathymetry.
    • Surface currents to account for wave refraction, resulting in reduced smoothing of wave fields.

  • Atmospheric analysis:

    • EDA resolution reduction and scale-selective re-centring addresses issues with tropical cyclone initialisation.  Helps avoid analysis of unrealistic 'double-centred' pattern.

  • Snow and land-ice:

    • New ice parametrisation scheme included in ecLand.  This gives more realistic representation of snowpack properties over glaciers and ice-sheets.  Replaces the previous binary glacier mask. 
    • The albedo of land-ice is fixed to 0.4 to account for the impurities and debris on the ice. 
    • Dynamic albedo to account for decreased albedo for near-melting conditions.  
    • Additional melting of snow and ice over glacier points.
    • Runoff generated from the ice melt is added to the surface runoff over the grid-box.
    • Snow (single layer representation) on land-ice tile.  Reduces the warm bias in winter over ice surfaces, especially in cloud free situations
    • Modified Stochastically Perturbed Parametrisation (SPP) to reduce 10-metre wind spread in the ensemble and related misalignment of wind speed and wave height in perturbed members.

  • Model physics:

    • Convection and microphysics changes to improve the propagation of precipitation from ocean across land.   Some of the convective precipitation is passed to the cloud scheme, where it is subject to advection and evaporation.   This improves penetration of maritime showers inland from the coast. 
    • Reduced vertical diffusion in stable conditions in the stratosphere.
  • Ocean-atmosphere coupling:
    • Effect of variable snow depths and sea-ice thicknesses in sea-ice model represented in the atmospheric model.
    • Fully coupled ocean-atmosphere forecasts.  The atmosphere now uses sea surface temperatures (SSTs) directly from the ocean model 

Meteorological impact

  • Medium Range

    • Improvements to forecasts of light precipitation.
    • Better representation of convective precipitation; the revised convection / cloud-microphysics scheme reduces “stationary” convective precipitation, improving inland propagation of rainfall.
    • Improved tropical upper-air temperature and wind forecasts (at 850 hPa and 250 hPa) by up to ~7%, thanks to updates in aerosol climatology, convection, and physics ordering.
    • Improvement of temperature and humidity forecasts around the tropopause due to assimilation of stratospheric humidity from radiosondes up to 60 hPa.
    • Reduction of the known SST warm bias in the Southern Ocean  
    • Improved Western Boundary Currents (e.g. Gulf Stream), and related large SST biases. 
    • Dynamic evolution of marine variables (e.g. SST/SIC) in the analysis consistent with validity time
    • Forecasts of total cloud cover, dewpoint temperature and 10-metre winds over sea improved by 1-2%, largely due to changes in the physics of the model
    • Reduced ensemble wind spread at 10 m.

  • Sub-seasonal range

    • Increased forecast skill for quasi-biennial oscillation (QBO) in tropical stratospheric winds; stronger amplitude and more realistic vertical descent.
    • More realistic stratospheric dynamics. 


(FUG Associated with Cy50r1)











  • No labels