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ECMWF ERA5: ensemble means of surface level analysis parameter data

Update Frequency: Monthly
Latest Data Update: 2023-06-07
Status: Ongoing
Online Status: ONLINE
Publication State: Published
Publication Date: 2021-12-13
Download Stats: last 12 months
Dataset Size: 1.3M Files | 2TB

This dataset has been superseded. See Latest Version here

This dataset contains ERA5 surface level analysis parameter data ensemble means (see linked dataset for spreads). ERA5 is the 5th generation reanalysis project from the European Centre for Medium-Range Weather Forecasts (ECWMF) - see linked documentation for further details. The ensemble means and spreads are calculated from the ERA5 10 member ensemble, run at a reduced resolution compared with the single high resolution (hourly output at 31 km grid spacing) 'HRES' realisation, for which these data have been produced to provide an uncertainty estimate. This dataset contains a limited selection of all available variables and have been converted to netCDF from the original GRIB files held on the ECMWF system. They have also been translated onto a regular latitude-longitude grid during the extraction process from the ECMWF holdings. For a fuller set of variables please see the linked Copernicus Data Store (CDS) data tool, linked to from this record.

Note, ensemble standard deviation is often referred to as ensemble spread and is calculated as the standard deviation of the 10-members in the ensemble (i.e., including the control). It is not the sample standard deviation, and thus were calculated by dividing by 10 rather than 9 (N-1). See linked datasets for ensemble member and ensemble mean data.

The ERA5 global atmospheric reanalysis of the covers 1979 to 2 months behind the present month. This follows on from the ERA-15, ERA-40 rand ERA-interim re-analysis projects.

An initial release of ERA5 data (ERA5t) is made roughly 5 days behind the present date. These will be subsequently reviewed ahead of being released by ECMWF as quality assured data within 3 months. CEDA holds a 6 month rolling copy of the latest ERA5t data. See related datasets linked to from this record. However, for the period 2000-2006 the initial ERA5 release was found to suffer from stratospheric temperature biases and so new runs to address this issue were performed resulting in the ERA5.1 release (see linked datasets). Note, though, that Simmons et al. 2020 (technical memo 859) report that "ERA5.1 is very close to ERA5 in the lower and middle troposphere." but users of data from this period should read the technical memo 859 for further details.

Citable as:  European Centre for Medium-Range Weather Forecasts (2021): ECMWF ERA5: ensemble means of surface level analysis parameter data. Centre for Environmental Data Analysis, date of citation.
Abbreviation: Not defined
Keywords: ECMWF, ERA, ERA5, reanalysis, analysis, surface level, ensemble run


Previous Info:
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Previously used record identifiers:
No related previous identifiers.
Access rules:
Access to these data is available to any registered CEDA user. Please Login or Register for an account to gain access.
Use of these data is covered by the following licence: When using these data you must cite them correctly using the citation given on the CEDA Data Catalogue record.
Data lineage:

Data are generated by the ERA5 project at European Centre for Medium-Range Weather Forecasts (ECMWF) before being prepared by CEDA staff using the ECMWF system and uploaded to Centre for Environmental Data Analysis (CEDA) for ingestion into the archive. Data are translated over to a regular latitude-longitude grid and converted to netCDF format ahead of transfer to the CEDA system.

Data Quality:
ECMWF quality controlled data.
File Format:
Data are netCDF formatted.

Process overview

This dataset was generated by the computation detailed below.

ECMWF ERA5 Re-analysis Model deployed on ECMWF Computer


This computation involved: ECMWF ERA5 Re-analysis Model deployed on ECMWF Computer. The data assimilation system used to produce ERA5 is based on the Integrated Forecasting System (IFS)Cycle 41r2 release, with several added features specifically developed for reanalysis. The many changes and improvements incorporated into the IFS represent a decade of research and development in modelling and data assimilation. The ERA5 reanalysis benefits from research conducted in the EU-funded ERA-CLIM and ERA-CLIM2 projects carried out by ECMWF and partners. These led to improved input data for the assimilating model that better reflects observed changes in climate forcings, as well as many new or reprocessed observations for data assimilation.

The system includes :

- Model input: Appropriate for climate (e.g. CMIP5 greenhouse gases, volcanic eruptions,
SST and sea-ice cover)
- Spatial resolution: 31 km globally, 137 levels to 0.01 hPa
- Uncertainty estimates - From a 10-member Ensemble of Data Assimilations (EDA) at 63 km resolution
- Output frequency: Hourly analysis and forecast fields, 3-hourly for the EDA
- Input observations: As in ERA-40 and from Global Telecommunication System. In addition, various newly reprocessed datasets and recent instruments that could not be ingested in ERA-Interim
- Variational bias scheme: Satellite radiances and also ozone, aircraft and surface pressure data
- Satellite data: RTTOV-11, all-sky for various components
- Additional innovations: Long-term evolution of CO2 in RTTOV, cell-pressure correction SSU, improved bias correction for radiosondes, EDA perturbations for sea-ice cover

Input Description


Output Description


Software Reference


  • units: m s**-1
  • long_name: 10 metre U wind component
  • var_id: u10
  • units: m s**-1
  • long_name: 10 metre V wind component
  • var_id: v10
  • units: K
  • long_name: 2 metre dewpoint temperature
  • var_id: d2m
  • units: K
  • long_name: 2 metre temperature
  • var_id: t2m
  • units: Pa
  • var_id: msl
  • long_name: Mean sea level pressure
  • standard_name: air_pressure_at_mean_sea_level
  • standard_name: sea_ice_area_fraction
  • units: (0 - 1)
  • long_name: Sea ice area fraction
  • var_id: siconc
  • units: K
  • var_id: sst
  • long_name: Sea surface temperature
  • units: K
  • long_name: Skin temperature
  • var_id: skt
  • standard_name: cloud_area_fraction
  • units: (0 - 1)
  • long_name: Total cloud cover
  • var_id: tcc
  • units: kg m**-2
  • long_name: Total column water vapour
  • var_id: tcwv
  • standard_name: lwe_thickness_of_atmosphere_mass_content_of_water_vapor
  • units: degrees_north
  • var_id: latitude
  • long_name: latitude
  • units: degrees_east
  • var_id: longitude
  • long_name: longitude
  • long_name: time
  • var_id: time

Co-ordinate Variables

Temporal Range
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Geographic Extent