Description of the upgrade

IFS Cycle 43r3 is an upgrade with many scientific contributions, including changes in data assimilation (both in the EDA and the 4D-Var), in the use of observations, and in modelling. The new cycle only includes meteorological changes; there are no technical changes, e.g. new resolutions.Model changes include a new radiation scheme, improvements in the modelling of convection and a new aerosol climatology.

Changes in data assimilation and in the way dropsonde observations are handled have improved the accuracy of the initial conditions on which forecasts are based. This is especially true of tropical cyclones.

This upgrade of ECMWF’s Integrated Forecasting System (IFS) improves forecast skill in medium-range and monthly forecasts. 

News

Timeline of the implementation

The planned timetable for the implementation of the cycle 43r3 is as follows:

The timetable represents current expectations and may change in light of actual progress made.

Datasets affected

• HRES
• ENS
• HRES-WAM
• HRES-SAW
• ENS-WAM

Resolution

Unchanged from previous IFS cycle.

Meteorological content of the new cycle

Assimilation

• • Improved humidity background error variances directly from the EDA like for all other variables.
  • Revised wavelet filtering of background error variances and revised quality control of drop-sonde wind observations in 4DVAR to improve tropical cyclone structures.

Observations

• • Increased use of microwave humidity sounding data by adding new sensors (SAPHIR, GMI 183 GHz channels).
  • Activation of 118 GHz channels over land from MWHS-2 instrument on-board FY-3C.
  • Harmonised data usage over land and sea-ice for microwave sounders (adding MHS channel 4 over snow, adding some ATMS channels, lower observation errors for MHS data over land).
  • Improved screening of infrared observations for anomalously high atmospheric concentrations of hydrogen cyanide (HCN) from wildfires.
  • Improved quality control for radio occultation observations and radiosonde data.

Model

• • New, more efficient radiation scheme with reduced noise and more accurate longwave radiation transfer calculation.
  • New aerosol climatology based on ‘tuned’ CAMS aerosol re-analysis including dependence on relative humidity.
  • Increased super-cooled liquid water at colder temperatures (down to -38C) from the convection scheme.
  • Visibility calculation changed to use ‘tuned’ CAMS aerosol climatology.

Meteorological impact of the new cycle

Upper air

Results for the HRES from alpha- and beta-testing are positive, with many of the scores over NH, SH and Europe indicating statistically significant improvements at the 95% level up to about forecast day 5 when forecasts are verified against own analysis. When forecasts are verified against observations, the positive impact of 43r3 is also evident. Improvements are larger in summer than in winter and are to a large extent due to improvements in the humidity background error, as well as changes to the deep convection scheme and the aerosol climatology, which improved the temperature gradient between extra-tropics and tropics. Improvements are significant for temperature and vector wind throughout the extra-tropical troposphere. In the tropics there is some deterioration in temperature and humidity at certain vertical levels associated with the changes to the deep convection scheme. Surface parameters show partially statistically significant improvements both in the tropics and extra-tropics (2-m humidity, 10-m wind speed, total cloud cover, precipitation), except for 2-m temperature which shows neutral results.

Weather parameters and waves

Over the ocean, statistically significant improvements are seen for verification against own analysis for 10-m wind speed, significant wave height, and mean wave period.

Ensemble

Results for the ENS based on alpha-testing are mainly positive and similar to the HRES both for upper-air and surface variables for the NH, SH, and Europe when verified against analysis. In the tropics there is some deterioration in upper tropospheric wind speed and lower tropospheric temperature associated with reduced spread. There are also some slight deteriorations in tropical 2-m temperature and precipitation scores.

Tropical cyclones

Changes in the tropical cyclone analysis are notable, with the cyclone structure defined in a better way. At forecast day 1 there is a marginally significant improvement in position error; the improvement is undetectable thereafter. Tropical cyclone intensity (as measured by central pressure) is slightly reduced from day 2 onwards: for lead times beyond four days this has a beneficial effect since it reduces the existing negative bias in tropical cyclone central pressure in such forecasts. You can find statistics on the Cycle 43r3 tropical cyclones forecast performance in  TCPerformance_43r3_43r1.pdf.

Evaluation

Comparison of scores between IFS cycle 43r3 and IFS cycle 43r1 for HRES and ENS can be found in the IFS Cycle 43r3 scorecard. 

New and changed parameters

New parameters

There are no new parameters introduced with IFS Cycle 43r3.

Re-forecasts

The re-forecasts for the cycle 43r3 are computed from 8 June 2017. Therefore, the model climate used for the Extreme Forecast Index and other products is using a mixture of cycle 43r1 and cycle 43r3 re-forecast data. We will have a model climate fully based on cycle 43r3 date by 22 June 2017, in time before the implementation date of the new cycle. Users planning to build a model climate using the cycle 43r3 test re-forecasts will also need to include cycle 43r1 re-forecast data during the following weeks.

Technical content

Changes to GRIB encoding

Model identifiers

The GRIB model identifiers (generating process identification number) for cycle 43R3 will be changed as follows:

Software

The versions of EMOSLIB and GRIB API used to decode the existing operational cycle 43r1 data are suitable to handle the cycle 43r3 data as well.

Availability of test data from the cycle 43r3 test suites

Test data in MARS

IFS data from the cycle 43r3 suites is available in MARS with E-suite experiment version (expver) 0071 (MARS keyword EXPVER=0071) starting from 26 March 2017 at 06UTC.

The data can be accessed in MARS from:

• HRES (class=od, stream=oper, expver=71)
• Wave HRES (class=od, stream=wave, expver=71)
• ENS (class=od, stream=enfo, expver=71)
  • 00 UTC cycle only before 07 June 2017
• ENS Wave (class=od, stream=waef, expver=71)
  • 00 UTC cycle only before 07 June 2017

Only registered users of ECMWF archiving 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 User Support.

Test data in dissemination

IFS Cycle 43r3 test data from the release candidate testing stage is available through the test dissemination system. Users of ECMWF dissemination products can trigger transmission of test products by logging in to the test ECPDS system at https://ecpds-xmonitor.ecmwf.int/   in the usual manner. In order 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 ) 193.61.196.113 ( ecpds-xmc.ecmwf.int )
  

• RMDCN transfers: 136.156.8.132 ( mspds-dm4.ecmwf.int )

The IFS Cycle 43r3 test products are available as version number 71 (file names ending with '71'). The test products are generated daily, shortly behind real-time from both the 00UTC and 12UTC runs and based on the operational dissemination requirements and the IFS Cycle 43r3 test data for HRES, ENS, HRES-WAM, ENS-WAM and HRES-SAW.

Should you require any assistance with IFS Cycle 43r3 test dissemination products, Member and Cooperating states should contact Unknown User (maj) and Commercial customers should contact Data Services.

 Graphical display of IFS cycle 43r3 test data using ecCharts

Forecast users can use ecCharts to inspect the IFS Cycle 43r3 test data and compare with the operational forecast.  This facility is provided for testing purposes: the 43r3 test charts should not be relied upon for operational forecasting. Note in particular that the availability and timeliness of the cycle 43r3 test data will vary, and can be delayed with respect to the operational schedule.

IFS Cycle 43r3 test data is accessible via the ecCharts layers menu, identified by the label "(Esuite: 0071)".

Web charts based on IFS cycle 43r3 test data

Web charts based on IFS cycle 43r3 test data are available. They can be viewed by first selecting the chart in the Charts Catalogue, and then choosing the Model run tab above the chart, then selecting "New cycle (IFS 43r3)". The chart types which have 43r3 data available are those for which the icon representing the chart includes a grey arrow, as illustrated hereafter:

All these charts are clickable. Note that if you click on a Cycle 43r3 chart then the location products you see, such as meteograms, will be generated from that suite. If you change back on the Model run tab to operational, then click "OK" on the location product window, the product will be re-created using operational model data.

ENS meteograms based on IFS cycle 43r3 test data

ENS Meteograms based on IFS cycle 43r3 test data are available.  They can be plotted by choosing 'New cycle (IFS 43r3)' under the tab named 'Model run' on the  interactive ENS meteogram page 

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 43r3 test data by using the special 'events' set up for this purpose:

For these events, MSJ_EXPVER environment variable is set to 0071 and can be used to specify the IFS Cycle 43r3 test data any MARS retrievals.

These events are  intended for testing technical aspects only and should not be used for operational forecasting.

Options 2 and 3

Option 2 or 3 time-critical applications can be tested with the  IFS Cycle 43r3 test data retrieved from MARS or received in Dissemination.

Resources

• ECMWF Newsletter Number 152: https://www.ecmwf.int/en/newsletter/152/meteorology/ifs-cycle-43r3-brings-model-and-assimilation-updates
• Flemming, J., Benedetti, A., Inness, A., Engelen, R. J., Jones, L., Huijnen, V., Remy, S., Parrington, M., Suttie, M., Bozzo, A., Peuch, V.-H., Akritidis, D., and Katragkou, E.: The CAMS interim Reanalysis of Carbon Monoxide, Ozone and Aerosol for 2003–2015, Atmos. Chem. Phys., 17, 1945-1983, doi:10.5194/acp-17-1945-2017, 2017.
• Hogan, R., and Bozzo, A., 2016: ECRAD: A new radiation scheme for the IFS. ECMWF Research Department Technical Memorandum No. 787, pp 33. Available at http://www.ecmwf.int/sites/default/files/elibrary/2016/16901-ecrad-new-radiation-scheme-ifs.pdf.

Document versions