Description of the upgrade

The IFS Cycle 49r1, will bring major changes to the IFS model and data assimilation system, including among many others:

• assimilation of 2m temperature observations, 
• Land-surface model updates,
• increased resolution and soft-recentering of the ensemble of data assimilations (EDA)  and
• activation of the stochastically perturbed parameterisations (SPP) model uncertainty scheme in all ensemble configurations. 

Extended-range forecast will change name to sub-seasonal range forecast. This name change will be gradually implemented in the documentation.

The re-forecasts for medium and sub-seasonal forecast systems will see a change in frequency; whilst both will span the past 20 years, as before, they will now be run for fixed days of the month: 

• medium range every four days: 1/5/9/13/17/21/25/29 (excluding 29 February)
• sub-seasonal range every two days: 1/3/5/7/9/11/13/15/17/19/21/23/25/27/29/31 (excluding 29 February)

In IFS Cycle 49r1, HRES and the ENS control forecast become scientifically and computationally identical and both are run for 15-days at 00 UTC and 12 UTC, and 6 days at 06 UTC and 18 UTC. The superfluous ENS control forecast will be stopped in a future IFS upgrade, and the data stream currently known as HRES will become known as the “control” forecast.

From IFS Cycle 49r1 the wave model will be run on the same octahedral reduced gaussian grid as the atmospheric model, simplifying the data exchange between the two systems. Consequently the resolution of the wave model will increase to ~9km (O1280) in the medium range and ~36 km (O320) in the sub-seasonal range. With higher resolution, the wave model is better able to capture the atmospheric forcing, and details of the coastal conditions are generally better represented. The wave model will also run for 15-days at 00 UTC and 12 UTC, and for 6 days at 06 UTC and 18 UTC.
The wave spectrum continues to be discretised with 36 frequencies and 36 directions. However, to reduce the data volume, please note that in Cycle 49r1 only the first 29 frequencies will be output spanning a range from ~0.035 Hz to ~0.5 Hz.

More detailed information will be made available in the coming weeks.

Fo r any questions, please contact us via the ECMWF Support Portal .

#IFS49r1 #newfcsystem @ECMWF

News

Timeline of the implementation

Datasets affected

• HRES (day 1-15)

• ENS (day 1-15)

• ENS sub-seasonal (previously 'extended') (day 1-46)

• HRES-WAM (day 1-15)

• ENS-WAM (day 1-15)

• ENS-WAM sub-seasonal (previously 'extended') (day 1-46)

Resolution

Resolutions in bold increased/changed from the previous operational IFS cycle.

Dissemination schedule

The dissemination schedule will change for both the medium range and sub-seasonal range re-forecasts.

Medium range re-forecasts will be produced and disseminated every four days starting with 1st of every month:   1/5/9/13/17/21/25/29 (excluding 29 February)

Sub-seasonal range re-forecasts will be produced and disseminated every odd day of the month: 1/3/5/7/9/11/13/15/17/19/21/23/25/27/29/31 (excluding 29 February)

Meteorological content

Assimilation

• An upgrade of the Radiative Transfer for TOVS (RTTOV) model to version 13.2, which includes a new neural network-based surface emissivity model (SURFEM) trained on the reference Passive and Active Reference Microwave to Infrared Ocean (PARMIO) model.   ​

• Non-microwave satellite observation package ​

• T2m assimilation package (read more in the article: Model upgrade will bring better two-metre temperature forecasts) ​

• VarQC and stratospheric balance assimilation package

• Activation of Variational Quality Control (VarQC) in the first 4D-Var minimization ​

• Land-surface assimilation package

• Assimilation of altimeter wave height data will be done in hourly sequential windows rather than 6‑hourly ones

• Updates to ensemble of data assimilations (EDA)

  • the horizontal grid-spacing of the EDA outer loop resolution is reduced to ~9 km and the inner-loop grid-spacing is reduced from ~100 km to ~40 km

  • soft-recentering of each member (1 outer loop) around a more accurate control member (3 outer loops)

Observations

• Several updates to non-microwave observations, including
  • reduced thinning of Spinning Enhanced Visible and InfraRed Imager (SEVIRI) data, and
  • scene dependent observation errors for Cross-track Infrared Sounders (CrIS, NPP and NOAA-20)
• The Global Navigation Satellite System Radio Occultation (GNSS-RO) assimilation is extended in the vertical from 50 km to 60 km in altitude. Based on a tuneable GNSS-RO observation uncertainty model, the 3 microradian lower limit for the observation error standard deviation in the middle and upper stratosphere is reduced to 2.25 microradians for GRAS and COSMIC-2 (from 3 microradians). This increase in GNSS-RO observation usage and weight improves their efficacy as anchor observations in the stratosphere, knowing that only GNSS-RO, AMSUA and ATMS are currently sensing the 50-60 km layer.

Model

• Wave model and convection package (read more in the article: Ocean wind wave model upgrade improves the forecasting system)

• Land-surface model updates (read more in the article: An urban scheme for the IFS)

• Activation of the Stochastically Perturbed Parametrisations (SPP) scheme, which replaces the effective but long-serving Stochastically Perturbed Parametrisation Tendencies (SPPT) scheme in all ensemble configurations

• Physics and numerics contributions

• Atmospheric composition package

Meteorological impact

Medium range

• 2m temperature and 10m wind speed forecasts are improved in short and medium-range.
  • The largest impacts on 2m temperature forecasts are for the winter months in the northern hemisphere, where the Continuous Ranked Probability Score (CRPS) is improved by 11% at day 1 and 2% at day 10.
  • Forecasts of 10 m wind speed are improved throughout the year. The largest impacts are for the winter months of the northern hemisphere, where the CRPS is improved by 12% at day 1 and 6% at day 10
• Increased spread in Tropical Cyclones – beneficial for strong systems.

Sub-seasonal range

• The most robust impacts on weekly mean forecast anomalies are small but statistically robust changes in the ensemble spread, which are driven by the switch from SPPT to SPP

• Positive impact on Madden-Julian Oscillation (MJO) at week 3-4

Evaluation

Interactive scorecards presenting the new cycle performance are coming soon.

Key configuration changes

Atmospheric model

• HRES and ENS Control run will be computationally identical.

• Both HRES and ENS will run:

  • to day 15 (step 360) for the 00 and 12 runs, and

  • to day 6 (step 144) for the 06 and 18 runs (as part of BC Optional Programme)

• There will be no change in vertical or horizontal resolution of the Atmospheric mode l 

• There will be no ENS configuration changes

• Medium range hindcast and Medium range hindcast statistics will be produced every four days starting from 1st of every month: 1/5/9/13/17/21/25/29 (excluding 29 February)
• Sub-seasonal hindcast and Sub-seasonal hindcast statistics will be produced every odd day of the month: 1/3/5/7/9/11/13/15/17/19/21/23/25/27/29/31 (excluding 29 February)

Wave model

• With IFS Cy49r1, the wave model will be run on the same grid as the atmospheric model, simplifying the data exchange between the two systems.  This means that the native grid for ENS-WAM will change from the 14km reduced lat-lon grid with 0.125° latitudinal spacing to the 9km O1280 octahedral reduced Gaussian grid.
• The wave spectrum on the O1280 grid continues to be discretised with 36 frequencies and 36 directions. However, to reduce the data volume, please note that in Cycle 49r1 only the first 29 frequencies will be output spanning a range from ~0.035 Hz to ~0.5 Hz.
• For users receiving parameter 2DFD via Dissemination, the number of frequencies will be adjusted automatically in the data requirements in the test system.  Users requesting 2DFD from MARS will need to adjust the number of frequencies in their retrieval requests.

• WAM and WAM sub-seasonal grid resolution will be the same as that of the corresponding ENS and ENS sub-seasonal. For the native grid, this means:
  • Medium range wave model will increase from a 14km reduced lat-lon grid with 0.125° latitudinal spacing to the 9km O1280 octahedral reduced Gaussian grid.
  • Sub-seasonal wave model will increase from a 55km reduced lat-lon grid with 0.125° latitudinal spacing to the 36km O320 octahedral reduced Gaussian grid.
• The number of frequencies output will be 29, spanning a range from ~0.035 Hz to ~0.5 Hz .
• For users receiving parameter 2DFD via Dissemination, this will be automatically adjusted in your data requirements in the test system.  Users requesting 2DFD from MARS will need to adjust the number of frequencies in their retrieval requests.

• The grid resolution of the medium range wave and sub-seasonal range wave hindcast and hindcast statistics will increase to match the corresponding medium and sub-seasonal forecast (Atmosphere)
• The production schedule of medium range wave and sub-seasonal range wave hindcast and hindcast statistics will match that of the medium range and sub-seasonal range hindcast and hindcast statistics of the Atmospheric model

Test data in MARS

IFS Cycle 49r1 beta test data is available from MARS with E-suite experiment version (expver) 0079 (MARS keywords EXPVER=0079, CLASS=OD): 

Medium range forecast

Atmospheric model

• Control forecast (former HRES) (stream = OPER)
• ENS (stream = ENFO)
• ENS hindcast (stream = ENFH)
• ENS hindcast statistics (stream=EFHS)

Wave model

• HRES-WAM (stream = WAVE)

• ENS-WAM (stream = WAEF)

• ENS-WAM hindcast (stream = ENWH)
• ENS-WAM hindcast statistics (stream = WEHS)

Sub-seasonal range forecast

Atmospheric model

• ENS sub-seasonal (former 'extended') (stream = EEFO)
• ENS Sub-seasonal (former 'extended') hindcasts (stream = EEFH)
• ENS Sub-seasonal (former 'extended') hindcast statistics (stream = EEHS)

Wave model

• ENS_WAM Sub-seasonal (former 'extended') (stream = WEEF)
• ENS-WAM Sub-seasonal (former 'extended') hindcasts (stream = WEEH)

Only users registered with access to MARS will be able to access these test data sets. The data should not be used for operational forecasting.  Please report any problems you find with this data via the    ECMWF Support Portal.

Test data in dissemination

Cycle 49r1 test data from the release candidate phase (RCP) are available through the test dissemination system, starting from the 00Z run on    26 Jul 2024.

Users with access to ECPDS and the Products Requirements Editor (PREd) can login to the test system at https://xdiss-monitor.ecmwf.int/   and  https://products.ecmwf.int/esuite/requirements/  and trigger the transmission of test products in the usual manner.

To receive the test products, users have to have their firewall open to the relevant ECPDS Data Movers:

INTERNET:

• • 136.156.192.0/26
  • 136.156.193.0/26

RMDCN:

• • 136.156.196.0/26
  • 136.156.197.0/26

The IFS Cycle 49r1 test products are available as version number 79 (file names ending with '79') and are intended to be generated shortly behind real-time. 

 If you wish to receive 49r1 test data automatically (regularly), please contact Data Services via the   Support Portal   . 

Users are strongly advised to check that their software applications and data processing chain can handle the test data.

Please note that in particular changes to the resolution, e.g. requesting ENS-WAM data with 0.1° resolution, will have a significant impact on the requested data volumes.

The new parameters of Cycle 49r1 listed above will become available in dissemination after the implementation date.

If you don't have access to the ECPDS system or (T)PREd or should require any assistance with IFS Cycle 48r1 test dissemination products, please contact us via the   Support Portal   .

Time-critical applications

Option 1 - simple time-critical jobs

During the Release Candidate Phase users of the  "Simple time-critical jobs" framework can test that their scripts will work with the IFS Cycle 49r1 test data by using the limited ECaccess 'events' set up for this purpose:

For these events, MSJ_EXPVER environment variable is set to 0079 and can be used to specify the IFS Cycle 49r1 test data in any MARS retrievals.

Users wishing to retrieve data for days 10 to 15 of the Control (ex HRES) forecast should use the e_ms360 event.

These events are intended for testing technical aspects only and should  not  be used for actual time-critical activities.

Options 2 and 3

Option 2 or 3 time-critical applications can be tested with the IFS Cycle 49r1 test data retrieved from MARS or received in Dissemination.

References

• Plans for high-resolution forecast (HRES) and ensemble forecast (ENS) control run, ECMWF In focus item, 5 March 2024

• Improved two-metre temperature forecasts in the 2024 upgrade .  Ingleby, B.,  Arduini G., Balsamo G., Boussetta S., Ochi K. (JMA), Pinnington E., D e Rosnay P., ECMWF Newsletter No 178 - Winter 2024

• Model upgrade will bring better two-metre temperature forecasts, ECMWF News item, 4 June 2024

• An urban scheme for the IFS, McNorton J., Balsamo G., ECMWF Newsletter No 175 - Spring 2023

• Developing an urban scheme for the IFS, ECMWF News item, 30 May 2023 
• Ocean-wave-related changes in the next model upgrade , Bidlot J., Janssen P., ECMWF Newsletter No 179 - Spring 2024

• Ocean wind wave model upgrade improves the forecasting system, ECMWF News item, 24 June 2024

• A new view of Earth’s land surface and clouds with the IFS, Schröttle, J., Lupu, C., Lopez, P., Gillies, P., Sahin, C., Canessa, A. (CNMCA), ECMWF Newsletter No 180 - Summer 2024
• Simulation of top-of-the-atmosphere visible reflectances with the IFS, Lupu C., Schröttle, J., Lopez, P .,  ECMWF Newsletter No 177 - Autumn 2023

Fo r any questions, please contact us via the  ECMWF Support Portal .