Description of the upgrade
In the IFS Cycle 47r2 single-precision for ENS (forecast up to day 46 and hindcast) and HRES (forecast) will be introduced. Moreover, the ENS vertical levels will be increased to 137 to bring it in line with HRES.
Users of ENS model levels (in particular users of Time-Critical Applications or customers retrieving or receiving model levels) are advised to check the Technical content below.
A set of 12 auxiliary surface fields will be added to the ENS control forecast.
This cycle will use WMO BUFR tables version 35 for Tropical Cyclone tracks in BUFR format. Furthermore, Tropical Cyclone tracks from the 06/18 UTC forecast cycles will be made available as WMO essential products, including graphical product. We encourage users of these BUFR data to take note of the Update to Tropical Cyclone tracks and test their decoding software.
Implementation scheduled for 6 UTC cycle on 11 May 2021
Page updated on:
#IFS47r2 #newfcsystem @ECMWF
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NEWS! Added a grib_filter rules file to convert 91 sparse ENS model level GRIB fields into consecutively numbered 91 levels
Recording of the webinar on Cycle 47r2 performance, products and technical aspects is now available
Final webinar, focusing on latest model verification, new products, handling of ENS model level increase in dissemination and technical aspects, has been scheduled for 16 April 2021 at 8:00 (UTC). Join the webinar Recording of the webinar on ENS model level handling in dissemination is now available |
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Implementation timeline
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Meteorological content
In this model cycle single precision for ENS (forecast up to d+46 and hindcast) and HRES (forecast) will be introduced. The idea to use single precision in the IFS emerged from a research project at the University of Oxford and was tested in the OpenIFS model, a portable version of the IFS for research and educational use at institutes and universities. Followed by further research carried out at Météo-France and ECMWF it was shown that it is possible to significantly reduce the arithmetic precision of many of the calculations performed in numerical weather prediction models without compromising the quality of weather forecasts. ‘Single precision’ forecasts have the advantage of being computationally less expensive than traditional ‘double precision’ forecasts. Such efficiency savings will greatly facilitate the introduction of higher-resolution ensemble forecasts and other model improvements in line with ECMWF’s Strategy to 2025. The article 'Progress in using single precision in the IFS' provides additional information.
Moreover, the ENS vertical levels will be increased to 137 to bring it in line with HRES.
Meteorological impact
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Evaluation of 47r2
The two changes at 47r2 were a reduction to single precision in our HRES and ENS forecasts and (with the computational savings made) an increase from 91 to 137 levels in the ENS forecast. Our deterministic and ensemble analyses, including background forecasts, remain at double precision, and so are unaffected.
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Score cards The change to single precision is neutral in terms of HRES skill (less than a 0.3% change is typical for the troposphere, and the frequency of statistically significant differences is in line with what one might expect by chance), but there are benefits of the increased levels in the ENS. The ensemble score card is overwhelmingly positive and statistically significant (occasional negative changes are small in magnitude.) Scorecards presenting the new cycle performance are regularly updated:
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New parameters
The table contains the list of parameters expected to be available with the model implementation. They will be available as part of the test data.
Param ID | Short Name | Name | Unit | Component & type | GRIB edition | Level type | MARS | Added to Catalogue | ecCharts | Dissemination |
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174096 | 2sh | 2 metre specific humidity | kg kg-1 | HRES AN FC | 1 | sfc | | | ||
aluvpi | UV visible albedo for direct radiation, isotropic component | (0-1) | ENS CF | 1 | sfc | | | |||
aluvpv | UV visible albedo for direct radiation, volumetric component | (0-1) | ENS CF | 1 | sfc | | | |||
aluvpg | UV visible albedo for direct radiation, geometric component | (0-1) | ENS CF | 1 | sfc | | | |||
alnipi | Near IR albedo for direct radiation, isotropic component | (0-1) | ENS CF | 1 | sfc | | | |||
alnipv | Near IR albedo for direct radiation, volumetric component | (0-1) | ENS CF | 1 | sfc | | | |||
alnipg | Near IR albedo for direct radiation, geometric component | (0-1) | ENS CF | 1 | sfc | | | |||
sdfor | Standard deviation of filtered subgrid orography | m | ENS CF1 | 1 | sfc | | | |||
sdor | Standard deviation of orography | m | ENS CF1 | 1 | sfc | | | |||
isor | Anisotropy of sub-gridscale orography | - | ENS CF1 | 1 | sfc | | | |||
anor | Angle of sub-gridscale orography | radians | ENS CF1 | 1 | sfc | | | |||
slor | Slope of sub-gridscale orography | - | ENS CF1 | 1 | sfc | | | |||
lsrh | Logarithm of surface roughness length for heat | - | ENS CF1 | 1 | sfc | | |
1 Available at step 0 only.
Changes to existing BUFR parameters
Obstype | Name | Component & type | BUFR edition | MARS | ecCharts | Dissemination |
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32 | Tropical Cyclone track | HRES/ENS | 3/4 |
Technical information is available at Update to Tropical Cyclone tracks.
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Increase of ENS vertical resolution to 137 model levels
With this cycle upgrade the number of vertical model levels in ensemble forecasts (ENS) increases from 91 to 137, bringing it to the same vertical resolution as HRES. The L137 model level definitions and the correspondence between the L91 and L137 model levels are available online. Please note that the L137 model level data cannot be converted back to GRIB edition 1 without the loss of information.
Users getting ENS data on model levels are advised to check their data requests and processing. Getting all model levels, 137 instead of 91, will increase the amount of data by a factor of 1.5. This will affect resources like disc space, array sizes, processing and transfer times. Users should adapt any limits and requirements, e.g. wallclock time, memory, accordingly.
Users who are currently retrieving all 91 model levels from MARS wishing to retrieve the same number of equivalent levels from Cycle 47r2 could specify
...
levtype=ml,
levelist=1/2/4/6/7/9/10/12/14/15/17/19/20/22/24/25/27/29/30/32/34/35/37/38/40/42/43/45/46/48/49/51/52/54/55/57/58/59/61/62/63/65/66/67/69/70/71/73/74/76/77/78/80/81/82/84/85/87/88/90/91/93/94/96/97/98/100/101/103/104/105/107/108/110/111/112/114/116/117/119/120/122/124/126/128/129/131/133/134/136/137,
...
in their MARS requests. Users getting specific model levels should revise their selection based on the correspondence between the L91 and L137 model levels.
Please note that retrieval of non-consecutively numbered model levels could cause issues in down-stream applications. Therefore all users of ENS model level data are urged to test their applications using the available test data as described below. Users facing problems with non-consecutively numbered model levels might find this grib_filter rules file useful to convert 91 sparse model level GRIB fields into consecutive 91 level data.
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Changes to GRIB encoding
The GRIB model identifiers (generating process identification number) for cycle 47r2 will be changed as follows:
GRIB 1 Section 1 Octets | GRIB 2 Section 4 Octets | eccodes key | Component | Model identifier | |
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47r1 | 47r2 | ||||
6 | 14 | generatingProcessIdentifier | Atmospheric model | 151 | 152 |
6 | 14 | generatingProcessIdentifier | Ocean wave model | 116 | 117 |
Changes to BUFR encoding.
A new BUFR sequence has been designed to accommodate the new TC information. Technical information is available at:
Update to Tropical Cyclone tracks
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Software
To handle the data of Cycle 47r2 we recommend to use the ECMWF software packages
ecCodes 2.21.0
Magics 4.6.0
Metview 5.11.1
which will become the default on ECMWF platforms on Wednesday 5 May 2021, see Change of default versions of ECMWF and third-party software packages - May 2021. Users are strongly encouraged to test their software applications and data processing chain with the new versions of the various software packages before this change.
The minimum ECMWF software packages to provide full support for the new IFS Cycle 47r2 are ecCodes 2.20.0, Magics 4.5.3 and Metview 5.10.2.
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Availability of IFS cycle 47r2 test data
The release candidate test data and products will be generated daily, shortly behind operational high resolution and ensemble runs and based on the operational dissemination requirements. The availability of the test data does not follow any strict schedule.
Test data in MARS
IFS Cycle 47r2 release candidate test data will be available from MARS with experiment version 0075 (MARS keyword EXPVER=0075) starting from the 00 UTC on
The data can be accessed in MARS from:
- HRES (class=od, stream=oper, expver=75)
- HRES-WAM (class=od, stream=wave, expver=75)
- ENS (class=od, stream=enfo, expver=75)
- ENS-WAM (class=od, stream=waef, expver=75)
Only registered users of ECMWF computing systems will be able to access the test data sets in MARS. The data should not be used for operational forecasting. Please report any problems you find with this data to Service Desk.
Test data in dissemination
IFS Cycle 47r2 test data from the release candidate stage will be available through the test dissemination system, starting from the 00Z run on . Users with access to ECPDS and the Products Requirements Editor (PREd) can login to the test system at https://ecpds-xmonitor.ecmwf.int/ (or https://msaccess.ecmwf.int:7443) 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 transfers: 193.61.196.104 ( ecpds-xma.ecmwf.int ), 193.61.196.105 ( ecpds-xmb.ecmwf.int ) and 193.61.196.113 ( ecpds-xmc.ecmwf.int )
RMDCN transfers: 136.156.8.132 ( mspds-dm4.ecmwf.int ) and 136.156.8.133 ( mspds-dm5.ecmwf.int )
Access to the test PREd is provided at https://apps.ecmwf.int/webapps/esuite/products/requirements/
The IFS Cycle 47r2 test products are available as version number 75 (file names ending with '75'). The test products are intended to be generated shortly behind real-time. The test products will be based on the operational dissemination requirements from and will be available for HRES, HRES-WAM, ENS, ENS-WAM and ENS extended.
The initial requirements in the test system will in general be identical to the operational requirements. Any model levels specified for ensemble forecasts (ENS) will be replaced by the corresponding levels in the new cycle according to the correspondence between the L91 and L137 model levels, e.g. levelist=1/2/3/4/5 in the operational system will be replaced with levelist=1/2/4/6/7 in the test system. This approach is also applied if all model levels are requested in the operational system, i.e. they will be replaced by the 91 corresponding levels in the new cycle rather than by all 137 levels from the new cycle. Via the test PREd users will be able to test the full range of model levels. Once Cycle 47r2 becomes operational, the same approach is applied, i.e. any specified model levels from the current ensemble forecasts (ENS) will be replaced by the corresponding levels in the new cycle. Any changes made in the test system will not be ported to operations on implementation day. Access to the operational PREd will be closed at 9 UTC on 10 May. Any changes to the operational requirements can be implemented after 10 UTC on 12 May. The test PREd will be closed on 28 May.
Please note that in particular changes to the number of model levels will have a significant impact on the requested data volumes. For more information please watch our webinar on ENS model level handling in dissemination.
If you don't have access to the ECPDS system or PREd or should you require any assistance with IFS Cycle 47r2 test dissemination products, please contact Data Services.
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Layers of IFS cycle 47r2 release candidate test data will become available in ecCharts on . Cycle 47r2 layers are identified by the label "0075" in their title and a black border around test data layers for better visual identification.
Web charts based on IFS cycle 47r2 test data
The ENS meteograms based on IFS cycle 47r2 release candidate test data will become available on . They can be viewed by selecting the "IFS cycle 47r2" model run in the ENS meteograms interface.
WMO Essential and Additional test data
IFS cycle 47r2 WMO Essential test data starting from the 00Z run on is available at ftp://wmo:essential@xpds.ecmwf.int and WMO Additional test data at ftp://xpds.ecmwf.int using the relevant WMO user id and password.
Time-critical applications
Option 1 - simple time-critical jobs
Member State users of the "Simple time-critical jobs" framework can test that their scripts will work with the IFS Cycle 47r2 test data by using the limited ECaccess 'events' set up for this purpose:
1633 | e_ms090 | At this stage, the e-suite step 090 (HRES-BC) has been generated. |
1634 | e_ms144 | At this stage, the e-suite step 144 (ENS-BC) has been generated. |
1635 | e_ms240 | At this stage, the e-suite step 240 (HRES) has been generated. |
1636 | e_ms360 | At this stage, the e-suite step 360 (ENS) has been generated. |
1638 | e_ms1104 | At this stage, the e-suite step 1104 (ENS extended) has been generated. |
1639 | e_msrefc | At this stage, the e-suite step refc (REFORECAST) has been updated. |
For these events, MSJ_EXPVER environment variable is set to 0075 and can be used to specify the IFS Cycle 47r2 test data in any MARS retrievals.
These events are intended for testing technical aspects only and should not be used for Time Critical activities.
Options 2 and 3
Option 2 or 3 time-critical applications can be tested with theIFS Cycle 47r2 test data retrieved from MARS or received in Dissemination.
Resources
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Introducing the IFS Cycle 47r2 model | ENS model level handling in dissemination | Cycle 47r2 - Performance, products and technical aspects | ||||||||||||
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- Peter D. Dueben, Michail Diamantakis, Simon Lang, Sami Saarinen, Irina Sandu, Nils Wedi and Tomas Wilhelmson. Progress in using single precision in the IFS. ECMWF Newsletter, 2018.
- Filip Vana, Glenn Carver, Peter D. Dueben, Simon Lang, Tim Palmer, Martin Leutbecher, and Deborah Salmond. Single-precision IFS. ECMWF Newsletter, 148, 2016