Overview

OpenIFS 48r1 is based on the ECMWF operational IFS cycle 48r1 which has been the ECMWF operational model since June 27th 2023 (see Model upgrade increases skill and unifies medium-range resolutions)

OpenIFS 48r1 is a significant scientific and technical upgrade from the previous OpenIFS 43r3v2 model release and includes, amongst other things, a moist physics upgrade, incorporation of multi-layer snow scheme,  inclusion of operational CAMS chemistry and many more updates to the model physics parametrizations. Technical upgrades includes a new build system (move from FCM to ecbuild/cmake), major restructure of the code, inclusion of the single column model (SCM) and inclusion of ifs-test

Anyone wishing to use OpenIFS must have a OpenIFS license (see the list of Licensed Institutes).

It is important to note that OpenIFS 48r1 will not produce the same results as the previous releases based on 43r3.

Support

Please report any issues or problems with this release to either the OpenIFS User Forums or openifs-support@ecmwf.int.

Model Documentation 

OpenIFS 48r1 is scientifically identical to the forecast model of IFS 48r1. For a full description of the IFS 48r1 operational model, please see IFS documentation, noting that Part I and II and any sections on Observations and Data Assimilation are not applicable to OpenIFS. 

Summary of scientific changes compared to OpenIFS 43r3v2

Details about changes to the operational IFS from cycle to cycle can be found on

  1.  ECMWF IFS model changes and/or 
  2.  Changes to the forecasting system, which is linked from (1)

Below is a summary of the scientific changes from IFS 43r3 to 48r1, which are relevant to OpenIFS.

45r1 – Cloud microphysics, soil physics

  • Improved numerics for warm-rain cloud microphysics and vertical extrapolation for semi-lagrangian trajectory;

  • Increased methane oxidation rate to improve (increase) water vapour in the stratosphere;

  • Improved representation of super-cooled liquid water in convection, and minor convection updates;

  • Correction of soil thermal conductivity formulation and addition of soil ice dependency;

  • Modified parameter for non-orographic gravity-wave drag scheme for 91 levels.

46r1 – Radiation and aerosol, convection 

  • Improvements in convection scheme (entrainment, CAPE closure, shallow convection);

  • Activate LW scattering in radiation scheme;

  • 3D aerosol climatology replaces 2D climatology;

  • Correct scaling of dry mass flux in diffusion scheme. 

47r1 – Albedo, ocean waves drag, quintic interpolation 

  • Surface albedo changes including: 1) the use of six climatological fields from MODIS, 2) a better handling of the spectrum from the MODIS datasets;

  • Total Solar Irradiance (TSI) and Green House Gases (GHG) timeseries are updated with more recent ones from CMIP6;

  • Quintic interpolation in the vertical for semi-Lagrangian advection;

  • The drag coefficient over the oceans is reduced for strong winds to account for observational evidences whereby the drag coefficient reduces sharply for high winds;

  • Stability corrections to the mid-level and deep convective closures (neutral) and reduced bounds for parcel perturbations.

47r3 – Moist physics upgrade

  • A more consistent formulation of boundary layer turbulence, shallow convection and sub-grid cloud including:

    • Simplified and more consistent treatment of sub-grid cloud saturation adjustment,

    • Consistent treatment of subgrid cloud from boundary layer turbulent mixing without separate statistical cloud scheme,

    • Consistent computation of mixing height for unstable turbulent boundary layer and convection scheme,

    • Change from double to single iteration of turbulent mixing scheme;

  • New method for computing inversion strength based on moist entropy for distinguishing stratocumulus and cumulus cloud;

  • Limit to convective overshoot based on tropopause stability;

  • New parametrized deep convection closure with an additional dependence on total advective moisture convergence;

  • Change from exponential-exponential cloud vertical overlap to random-exponential overlap in closer agreement with observations;

  • Include vapour deposition process for growth of falling snow particles;

  • Change from linear to cubic interpolation for cloud liquid, ice, rain and snow semi-Lagrangian departure point calculations, including 3D quasi-monotone limiter;

  • Interpolation of cloud and precipitation to radiation grid changed from in-cloud to grid-mean;

  • Inclusion of full supersaturation adjustment in the ensemble SPPT stochastic perturbations;

  • Mass-weighting and relaxation timescale introduced for ensemble SPPT stochastic perturbations;

  • Bug fix for vertical interpolation of 3D aerosol climatology;

  • Improved calculation of extinction coefficients for near-surface visibility in fog, rain and snow;

  • Revised gustiness parametrization;

  • Improved calculation of the peak wave period for multi-peaked ocean wave spectra.

48r1 – Multi-layer snow, climate fields, water and energy conservation, interactive ozone, freezing drizzle

  • Multi-layer snow scheme;

  • Revised climate fields – improved orographic fields for atmospheric drag;

  • Improved water and energy conservation (dynamics and physics);

  • Radiatively interactive prognostic ozone using new Hybrid-Linear Ozone (HLO) scheme;

  • New precipitation category - freezing drizzle and revised microphysical processes;

  • Revised computation of Semi-Lagrangian advection departure points;

  • New model top sponge layer formulation and semi-Lagrangian vertical filter;

  • Revised SPPT, removed cloud saturation adjustment from tendency perturbations.


Summary of technical changes compared to OpenIFS 43r3v2

  • OpenIFS 48r1 ECbuild/cmake build system
    • the build system has been changed from FCM to ECbuild/cmake. This change means that 
      • OpenIFS uses the same build system as the IFS and can therefore capitalise on the pre-existing build options such as enablling single and/or double precision 
      • Simplifies the creation of OpenIFS from IFS
    • Associated changes in OpenIFS build scripts, please see Build OpenIFS 48r1
  • OpenIFS 48r1 can be built using single and/or double precision
  • OpenIFS includes CAMS chemistry and aerosol as implemented in the corresponding IFS cycle, i.e. 48r1, by default
    • Thus, as well as an upgrade, this release consolidates OpenIFS and OpenIFS/AC into one single code base, with one development workflow.
    • More aligned with the IFS
  • OpenIFS 48r1 includes the single column model (SCM) and builds the SCM alongside the 3-D model by default
  • OpenIFS 48r1 includes ifs-test with
    • 21 t21 tests of forecast-only functionality with and without chemistry
    • 1 SCM test
    • ifs-test can be used to
      • validate the installation, i.e., validate the build and basic simulation capability
      • genarate "known good output" for a given system and compiler, which can be used to test any code changes

Experiment data and namelist changes

There have been a significant number of changes to the model namelists and initial data format compared to OpenIFS 43r3. It is recommended that users do not attempt to use OpenIFS 43r3 namelists with OpenIFS 48r1 but should obtain new experiment data and matching namelists suitable for model cycle 48r1.

The recommended way to obtain initial experiment data for forecast experiments with OpenIFS is to use the OpenIFS Data Hub. For any data requests that are currently not served by the Data Hub please contact OpenIFS support by emailing openifs-support@ecmwf.int.