ECMWF 40-year re-analysis data (ERA-40)

The ECMWF ERA-40 Re-Analysis Project consists of a number of climate datasets spanning the period mid-1957 to August 2002 using a consistent model. The data overlaps with the earlier ECMWF ERA-15 Re-analysis project (1979-1993). The broad objectives and partner organisations are presented in the ERA-40 background information.

The entire 6-hourly dataset is available from the BADC. The status of the ERA-40 archive page gives details of previous modifications to the archive and any relevant changes are documented on the news page.

Monthly mean data (6-hourly and diurnal) is available for most of the parameters held in the full archive.

The ECMWF used a spectral model to generate the ERA-40 dataset. The BADC archives the data at spectral T159 resolution data and on an N80 Reduced Gaussian grid. The data can also be converted to a regular latitude-longitude grid for both surface/single level fields. Users interested in regular gridded ERA-40 data should see the information on the ERA-40 Regular Gridded Data page which includes an overview of tools available.

Users that require 2.5° x 2.5° regular gridded data can access it via ECMWF's public data server.

Four types of upper air levels are archived:

• model levels,
• pressure levels,
• potential temperature levels and
• potential vorticity levels.

The parameters vary with the type of grid and level on which they are stored. The parameters page lists all the available variables for each grid type, level type and time period. Information on the different grid types and level types is also provided.

There is some additional forecast data available consisting of mainly moisture-related forecast fields for January and July 1985.

Please also read the quality of the ERA-40 data page that highlights some deficiencies in the data.

The NCAS Centre for Global Atmospheric Modelling (CGAM) at the University of Reading have produced a number of graphical plots of ERA-40 data that are publicly available.

The ECMWF datasets are for bona fide research purposes only and access is therefore restricted.

The BADC can only distribute the data to academic users within the UK, on a per person per project basis (i.e. all members on a same project who will be using the data must individually apply for access to the data). For this reason, we do not make the data available to anonymous users through these web pages.

In order to gain access to the data and accompanying software, please apply for access to ECMWF ERA datasets . The application form includes the Met Office agreement and ECMWF ERA agreement, to be returned to the BADC.

You will then be given access to ERA datasets (ERA-15, ERA-40 and ERA-Interim) via the Browse Archive pages of the BADC web-interface and from an account on the BADC computer (allowing FTP access to the data).

Users wishing to obtain the data from the Manchester (see explanation below) archive should follow the instructions above to obtain a user account and then contact Paul Berrisford at the University of Reading.

Note: German users may be able to access the data from the BADC under a reciprocal agreement with the Max-Planck Institute for Meteorology (MPI-M). German users will need to register with the MPI-M using this form which should be faxed to Model & Data on +49-40-41-17-34-00, before applying for access under this agreement through the BADC.

Under this reciprocal agreement, registered BADC users who are authorised to access the ERA data held at the BADC, may gain access to the ECMWF products held at MPI-M. Please contact data@dkrz.de for details.

Users from other countries may be able to access these data through their own national meteorological organisation.

The ERA-40 data currently resides in two separate archives:

• The standard BADC data archive (at the Rutherford Appleton Laboratory (RAL), Oxfordshire)
• An archive at the Manchester High-Performance Computing Centre (maintained and updated by Centre for Global Atmospheric Modelling (CGAM) at the University of Reading).

The reason for holding two separate data archives is to meet the requirements of two distinct groups of atmospheric (and other) scientists. The standard BADC archive will serve the data using formats and utilities that the majority of earth scientists can make use of. The Manchester archive (see the CGAM web site for more information), on the other hand, is aimed specifically at users of the modeling resources held on the high-performance computing systems. This data will be mainly used by members of UGAMP (the UK universities Global Atmospheric Modeling Programme).

The datasets are held at the BADC in their original GRIB format. The data can be accessed via FTP or via our web-interface.

Users interested in regular gridded ERA-40 data should see the information on the ERA-40 Regular Gridded Data page.

Registered users can now access parts of this dataset via the BADC Data Extractor. See the Data Extractor web page for more details.

The ECMWF now provides its own GRIB decoding software (GRIBEX) free from the ECMWF software pages. Documentation on other external software packages that can read GRIB.

Details about the ERA-40 datasets held at the BADC are available on the following topics:

• Grid resolution types (i.e. horizontal resolution).
• Level types (i.e. vertical resolution).
• Parameters.

Other useful documentation includes:

• The ERA-40 Project Report Series.
• Extensive ECMWF documentation on the ERA-40 project
• The precipitation in ERA-40 Report as part of the GEWEX-GPCP Workshop on Precipitation Analysis (ECMWF, March 11-13 2003, see page 42).
• Monitoring the ERA-40 production (including plots and validation information on observations, assimilation and analyses).
• Background to the ERA-40 project
.
• The ERA-40 Project Plan (postscript file).
• The ERA-40 Archive Plan detailing products (postscript file).
• ECMWF Newsletter (Summer/Autumn 2004) containing a lengthy article about ERA-40.
• Proceedings from the Workshop on Re-analysis, November 5-9 2001.
• The ERA-40 Atlas, describing the climate during 1979-2001, is available from the ECMWF web site.

There is also documentation available via our ECMWF Operational data web pages detailing the Integrated Forecasting System that is used for operational forecasts. An ECMWF document entitled The description of the evolution of the ECMWF forecasting system and corresponding archive (published November 1999) is also available in .pdf format.

The ECMWF home page is available here:ECMWF home page.

The BADC holds other ECMWF datasets: ECMWF Operational data, ECMWF ERA-15 Re-analysis data and ECMWF ERA Interim data.

The BODC also has instrumentally recorded wave data available through their National Oceanographic Database, see here for further information. These data should be of interest to those users using the ERA 40 wave data held here at the BADC. Their holdings include entries for directional wave spectra, one-dimensional wave spectra and short-term statistics.

European Centre for Medium-Range Weather Forecasts. ECMWF ERA-40 Re-Analysis data, [Internet]. NCAS British Atmospheric Data Centre. 2006-, Date of citation. Available from http://badc.nerc.ac.uk/view/badc.nerc.ac.uk__ATOM__dataent_ECMWF-E40.

If you would like to know more about ERA-40 data and how to obtain it from the BADC, you should contact us through the BADC support line.Your query should be answered within one working day. When follow-up work is required, the BADC support will carry out the work as quickly and efficiently as possible, and in any case, the user will be kept informed of progress.

For information more directly related to the ERA-40 project and data, contact the ECMWF.