Difference between revisions of "ERA INTERIM"

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<span class="s1">The scripts used to convert the files from grib to netcdf are available in the checks github.<br/> [https://github.com/coecms/CollectionsScripts https://github.com/coecms/CollectionsScripts]</span>
<span class="s1">The scripts used to convert the files from grib to netcdf are available in the checks github.<br/> [https://github.com/coecms/CollectionsScripts https://github.com/coecms/CollectionsScripts]</span>

Revision as of 23:47, 1 May 2019

A subset of the ERA Interim re-analysis data ranging from 1979 to date are now hosted on the RDSI fast disk storage at NCI. This subset is currently managed by the ARCCSS. The original grib data is downloaded from the ECMWF server , it is regularly updated and specific variables are extracted and converted to monthly netcdf files. For more information on the original ECMWF collection visit their website: ERA-Interim page

ERA-Interim production will cease on the 31st of August 2019, so the complete span of ERA-Interim data will be from 1st January 1979 to 31st August 2019. Keeping in mind that ERA-Interim is published with an offset of about three months from the dataset's reference date, ERA-Interim August 2019 data will be made available towards the end of 2019.

Known issues

There are several known quality issues for the ERA Interim data, here is a list of web resources:

ERA Interim quality issues from ECMWF website

Climate Data Guide page on ERAI

Overview and re-analysis comparison from reanalyses.org

Some of these analysis are described more in depth in the following article: The ERA-Interim reanalysis: configuration and performance of the data assimilation system

We are listing all the issues we are aware of in this ERAI known issues page, please feel free to contribute, we just provide the data as it is downloaded from the ECMWF server, we do checks to make sure that our data is the same as the original but we cannot run checks for the original data.

We found very high values for temperature (~330-350 K) near the lower troposphere in the following periods: 26-31 Dec 2002 and 21-25 Dec 2003. Other variables might be similarly affected.


To comply with the ECMWF licensing you need to be registered with the ECMWF to use this data. To register with the ECMWF you have to sign the ERA Interim license and agreement.

NB: Users of the ECMWF data sets are requested to reference the source of the data in any publication, e.g. "ECMWF ERA-Interim data used in this study/project have been provided by ECMWF/have been obtained from the ECMWF MARS Data Server on <date>".
You also have to add the following paper to your references:

Data access

You can then request to join the ub4 project by using your NCI account to access | My NCI portal.
Remember you have to register with ECMWF before. Be aware that by requesting to be part of the ub4 project you are automatically agreeing to the ECMWF license agreement terms.


The data is available on raijin.nci.org.au under /g/data1/ub4/erai/grib for the grib version and /g/data1/ub4/erai/netcdf for the netcdf version.

  • Data Inventory: what's available and what we are downloading, regularly updated.

NB this is a new version of the inventory, includes more specific information on available variables. Please note that we download all the available surface fields, both analysis and forecast, but we don't convert all of them to netcdf, unless they are specifically requested. Just recently we added: three surface forecast fields: runoff, surface thermal radiation downwards, convective available potential energy (CAPE); three surface analysis fields: total cloud cover, high cloud cover, low cloud cover

The netcdf version is organized in monthly field files while the grib files have all the fields in one file.

The current netcdf version was released in April 2015, the previous version is still available in the ua8 project. If you request access before we moved the data to ub4, you are already part of ub4 and don't need to request access again to use the data. The older version is not updated anymore and we'll be kept there only for users who are at the ned of their project. In January 2016 we'll definitely delete the older version and anyone is encouraged to move to ub4, since this version is updated and is a better data product overall.

  • Monthly averaged fields

We stopped updating the monthly fields since the BoM has a copy of the same in their rr7 project. You can request access as for the other NCI projects on My NCI portal . Anyone working with the ARCCSS should be granted access, if you are having trouble getting access or the data you are looking for is not available there, let us know by e-mailing climate_help@nci.org.au .

Current netcdf version: v1.0

The main differences with the previous version, which is not anymore available, are:

1) netcdf4 format with compression, which allowed us to get rid of scale and offset

2) new filenames of the form <varname>_<frequency>_ERAI_historical_<level>_<from-date>_<to-date>.nc

Ex. : ta_6hrs_ERAI_historical_an-ml_20110101_20110131.nc

3) some of the variable names have changed to the correspondent CMIP5 standard name, all names are now lower cases

4) new directory structure /g/data1/ub4/erai/netcdf/<frequency>/<realm>/<level>/<version>/<variable>/files…

Ex. : /g/data1/ub4/erai/netcdf/6hr/atmos/oper_an_ml/v01/ta/

5) there is more metadata information in the files, in particular we adopted CF conventions and added standard_names wherever possible. We also added an attribute MD5 checksum for each variable, this can be use to check for data corruption by using ncks or nco

The reason for the changes in filenames and directory structure is to make both as much as possible compliant to the CMIP5 filename and DRS standards, so the entire collection could be accessible from the CWSlab. This should be tested and implemented in the next few months.

Most of the data will be in the "atmos" realm, with the exception of ERAI land which is is "land" and few ocean fields. And most files have "6hr" frequency, with the exception of the forecast data which has "3hr" frequency.

The scripts used to convert the files from grib to netcdf are available in the checks github.