Description of the upgrade
On 8 March 2016, ECMWF upgraded the horizontal resolution of its integrated forecasting system (IFS) including its high-resolution (HRES) and ensemble (ENS) forecasts. The upgraded horizontal resolution is about 9 km for the HRES and the data assimilation (the outer loop of the 4D-Var) and about 18 km for the ENS up to day 15 and about 36 km for the extended range (monthly). The resolution of the ensemble of data assimilations (EDA) is increased to 18 km.
Implemented: 8 March 2016.
Timeline of the implementation
The planned timetable for the implementation of IFS cycle 41r2 is as follows:
|4 Nov 2015||Initial announcement to Member States and other forecast users|
|8 Dec 2015||Availability of test data in dissemination|
|14 Jan 2016||Test data in dissemination available at upgraded resolution|
|9 Feb 2016||Update of default software versions at ECMWF|
|8 Mar 2016|
Expected date of implementation
The timetable represents current expectations and may change in light of actual progress made.
Resolutions in bold increased/changed from previous IFS cycle.
- See more information on the specification of the resolution changes.
- See more information on the horizontal resolution upgrade.
- See details of resolution changes.
- See Introducing the octahedral reduced Gaussian grid.
The main contents of IFS cycle 41r2 are:
- The horizontal resolution is increased by using a cubic reduced Gaussian grid (with spectral truncation denoted by TC) instead of the current linear reduced Gaussian grid (denoted by TL). With the cubic reduced Gaussian grid the shortest resolved wave is represented by four rather than two grid points. In addition, a new form of the reduced Gaussian grid, the octahedral grid, is used. The octahedral grid is globally more uniform than the previously used reduced Gaussian grid.
- The realism of the kinetic energy spectrum is significantly improved with more energy in the smaller scales due to a reduction of the diffusion and removal of the dealiasing filter, enabled by the change to using a cubic truncation for the spectral dynamics.
- There is a significant revision to the specification of background error covariances (B) used in the HRES data assimilation due to the increased resolution of the EDA and the introduction of scale-dependence of the hybrid B (climatological and EDA), thereby relying more on the EDA "errors of the day" for the smaller scales.
- There are improvements in the use and coverage of assimilated satellite data due to changes in observation selection and error representation (for GPS radio occultation data, all-sky microwave, AMSU-A, IASI and AMVs) and improved observation operators for radiance data from microwave sounders.
- The stability of the semi-Lagrangian scheme near strong wind gradients is improved, reducing noise downstream of significant orography and in tropical cyclones.
- The radiative heating/cooling at the surface is improved by introducing approximate updates on the full resolution grid at every timestep. This leads to a reduction in 2-metre temperature errors, particularly near coastlines.
- Additionally there are changes to the triggering of deep convection, non-orographic wave drag and improvements to the linear physics in the data assimilation (for gravity wave drag, vertical diffusion and the surface exchange).
- do not include any increase in the vertical resolution;
- do not apply to the ECMWF seasonal forecasts;
- do not apply to the standalone wave model (HRES-SAW);
- do apply to products from the Boundary Condition Optional Programme.
See more details of the meteorological content of cycle 41r2 ...
See details of meteorological impacts of Cycle 41r2.
for HRES and ENS can be found in the IFS cycle 41r2 scorecard.
New and changed parameters
See new and changed parameters within the technical changes section.
Summary of technical changes
- Resolution changes
- New grid: the octahedral grid, for both HRES and ENS. See Introducing the octahedral reduced Gaussian grid for further details.
- Changes to GRIB encoding
- Changes to forecast products
- increased field
- new model output parameters
- correction to solar zenith angle for the sunshine duration diagnostic
- correction to the interpolation method used for the precipitation type diagnostic
- Changes to software
- Atmospheric: 146
- Ocean wave: 111 (unchanged)
- Standalone ocean wave: 211 (unchanged)
- Malardel S., et al. 2016: "A new grid for the IFS", ECMWF Newsletter No.146 - Winter 2015/16 (pages 23-28).
- Hólm, E, et al. 2016: "New model cycle brings higher resolution", ECMWF Newsletter No.147 - Spring 2016 (pages 14-19).
|4 November 2015|
|8 December 2015|
|22 December 2015|
|23 December 2015|
|14 January 2016|
|10 February 2016|
|1 March 2016|
|10 March 2016|
|28 July 2016|
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