Implementation of GRIB API in IFS cycle 36r2

Operational Upgrades

Seasonal Forecast System 4 New cluster products Migration to GRIB 2 GRIB API in 36r2 Horizontal resolution increase Unified VarEPS-Monthly Prediction System Soil Hydrology Scheme in 32r3 Seasonal Forecast System 3

Related

User guide of ECMWF products History of ECMWF model's cycle changes Full scientific and technical documentation of the IFS

Manuals

GRIB API

Printable

Implementation of GRIB API

On Tuesday 22 June 2010 ECMWF upgraded its analysis and forecasting systems to IFS cycle 36r2.

With the introduction of IFS cycle 36r2, the GRIB API library replaced GRIBEX for encoding GRIB products from the ECMWF deterministic forecasting system, the Ensemble Prediction System (EPS), including the monthly extension to 32 days and the Boundary Condition Optional Project.

This upgrade does not:

• introduce GRIB edition 2 encoding for any fields;
• apply to the global and Mediterranean (European Shelf) Wave model;
• apply to the ECMWF Seasonal Forecasting System 3.

ECMWF has endeavoured to eradicate any differences with respect to GRIBEX packing. GRIB headers are unchanged except in one case described in detail below.

Decoding of ECMWF fields using GRIBEX will continue to work following the upgrade.

To enable Member States to ensure that their codes will be able to decode ECMWF GRIB products following the upgrade to IFS cycle 36r2, a comprehensive test data set has been made available both in MARS and in dissemination.

Member States are strongly encouraged to carry out their own tests using the test data to ensure that their own codes will be able to handle ECMWF fields following this upgrade and to report any issues encountered to .

This current migration from GRIBEX to GRIB API is a necessary preparatory step enabling a number of new GRIB options and features, some of which will be required in forthcoming planned changes of the IFS. Specifically, the planned upgrade of the vertical resolution in spring 2011 requires GRIB API for encoding of model level data in GRIB edition 2. See Migration to GRIB edition 2 for further details.

With the introduction of IFS cycle 36r2, the model number identifier (generating process identification number - GRIB Section 1, Product Definition Section, Octet 6) has been changed:

• for atmospheric model fields from 136 to 137;
• for global wave model fields from 104 to 105;
• for European Shelf (Mediterranean) wave model fields from 204 to 205.

• News
• Timetable
• Products affected by changes to GRIB headers
• Test data sets from pre-operational e-suite in dissemination
• Test data sets from pre-operational e-suite in MARS
• GRIB API Software
• Document versions

This document will be updated as required and was last changed on 23.06.2010.

For a record of changes made to this page please refer to Document versions.

A printable version of this page is available.

For further information and advice regarding the upgrade, or to report any problems with decoding the test data, please contact User Support .

News

23 June 2010

IFS cycle 36r2 was implemented successfully in operations on Tuesday, 22 June 2010.

The new IFS cycle will also be used for the first time in the monthly extension of the Ensemble Prediction System on Thursday, 24 June 2010.

15 June 2010

The planned implementation date of IFS cycle 36r2, in operations is confirmed as Tuesday, 22 June 2010.

The first run with the new cycle on 22 June will be the 06 UTC analysis and forecast in the Boundary Condition project, followed by the 12 UTC main forecast. The monthly forecast extension to the EPS will be run with this new IFS cycle for the first time on Thursday 24 June 2010.

19 May 2010

First announcement to Member States of the plans for implementation of IFS cycle 36r2 in the ECMWF operational forecasting system.

Timetable

The implementation of GRIB API in the ECMWF operational forecasting systems is planned as follows:

The timetable given here represents our current expectations and may have to be reviewed in light of the actual progress made.

Products affected by changes to GRIB headers

GRIB parameter 134, surface pressure (SP), is in cycle 36r2 generated directly by the IFS, instead of a separate post-processing application. As a result, the GRIB elements describing the latitude and longitude of the boundaries of the Gaussian grid are being rounded differently for this parameter. The change is due to the application generating the product and not the introduction of GRIB API. The rounding affects the third decimal number in the definition of the N320 grid used by the EPS, in products accessed from MARS or the FDB. The change should not affect users of the Centre’s dissemination system, as disseminated Gaussian grid products are repacked in a consistent way.

Test data sets from pre-operational e-suite in dissemination

Please note that generation of test dissemination products from the IFS cycle 36r2 e-suite ceased following operational implementation on 22 June 2010.

Test dissemination products from the IFS cycle 36r2 deterministic e-suite are now generated on a daily basis. Products are based on current operational dissemination requirements. Users with access to dissemination products can trigger transmission of test dissemination files, in the same manner as from the operational ECPDS, from the test ECPDS system at:

• https://ecaccess.ecmwf.int:7443/      (Internet)
• https://msaccess.ecmwf.int:7443/     (RMDCN)

Re-queued files will be transmitted from IP addresses 193.61.196.113 (Internet) and 136.156.8.132 (RMDCN). Member States should make sure their firewall / network devices are configured accordingly.

To avoid potential impact on the operational dissemination, Member States are strongly advised in the first instance to transmit the test dissemination products where possible using their Internet connection. Only for final pre-production testing should products be transmitted via the RMDCN.

Test EPS and Mediterranean (European Shelf) Wave Model products will be made available shortly.

Test data sets from pre-operational e-suite in MARS

To enable Member States to ensure that their codes will be able to decode ECMWF GRIB products following the upgrade to IFS cycle 36r2, a comprehensive test data set for 22 April 2010 has been made available in MARS. For the Ensemble Prediction system, this data set includes:

• model level data;
• the monthly extension to 32 days for the 00 UTC cycle.

These data sets are available only to registered ECMWF users with access to MARS or WebMARS.

• Deterministic atmospheric model (Class=od, Stream=da, Expver=47):
• 00 UTC and 12 UTC on 22 April 2010.
• Deterministic wave model (Class=od, Stream=wa, Expver=47):
• 00 UTC and 12 UTC on 22 April 2010.
• Ensemble Prediction System (Class=od, Stream=enfo, Expver=47):
• 00 UTC and 12 UTC on 22 April 2010.
• Includes model level data.
• 00 UTC cycle includes the monthly extension to 32 days.
• Ensemble Forecast Hindcast (Class=od, Stream=enfh, Expver=47):
• 00 UTC on 22 April 2010.
• Wave Ensemble Forecast (Class=od, Stream=waef, Expver=47):
• 00 UTC and 12 UTC on 22 April 2010.
• 00 UTC cycle includes the monthly extension to 32 days.
• Wave Ensemble Forecast Hindcast (Class=od, Stream=waeh, Expver=47):
• 00 UTC on 22 April 2010.
• Boundary Conditions atmospheric model - short cutoff (Class=od, Stream=scda, Expver=47):
  • 06 UTC and 18 UTC on 22 April 2010.
• Boundary Conditions wave model - short cutoff (Class=od, Stream=scwv, Expver=47):
  • 06 UTC and 18 UTC on 22 April 2010.

The test data sets are provided for technical testing purposes and should not be used for operational forecasting. Please report any problems you find with this data to User Support .

GRIB API Software

Although decoding of ECMWF fields using GRIBEX will continue to work following the upgrade to IFS cycle 36r2, users are encouraged to use the GRIB API library.

The latest version 1.9.0 of the GRIB API library is available for download at:

http://www.ecmwf.int/products/data/software/grib_api.html

The GRIB API Manual is available at:

http://www.ecmwf.int/publications/manuals/grib_api/

Document versions