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A reanalysis is necessary for initiation of each re-forecast.   Spacial resolution are generally different between reanalyses and the model version used to create the re-forecasts.

ERA5

ERA-5

ERA-5 ERA5 is an improved and more comprehensive ECMWF climate reanalysis and is the fundamental initialising analysis for re-forecasts.

ERA products are normally updated once per month and within three months of real-time.  Quality assurance processing is applied to ensure consistency by removal of biases in models and observations.   Preliminary daily updates of the dataset can be available to users within seven days of real time.   ERA5 ERA-5 is available for dates from 1979 and is being extended forward in near real time.

ERA5 ERA-5 provides:

  • a much improved representation of the troposphere.
  • an improved representation of tropical cyclones.
  • better global balance of precipitation and evaporation.
  • better precipitation over land in the deep tropics.
  • better soil moisture.
  • more consistent sea surface temperatures and sea ice.

There is a potential problem related to inconsistencies between the model climate initialised with ERA-5 and the current real-time forecast based on Cy48r1 which uses new glacier fields and multi-layer snow scheme.  This inconsistency will be addressed in 49r1.

ERA-Interim (replaced by ERA-5 in 2019)

ERA-Interim is ECMWF's previous atmospheric reanalysis, based on a 2006 version of the IFS.  ERA-Interim data are available for dates from 1979 until 31st August 2019 but are no longer updated.  ERA5 ERA-5 replaced ERA-Interim in 2019.

The main differences of ERA5 ERA-5 from ERA-interim are

    • higher spacial resolution (137 levels, 31km; 62km for EDA).
    • higher output frequency of analysis fields (hourly, 3-hourly for EDA).
    • introduction of uncertainty estimates.
    • additional input observation types.
    • many more output parameters.
    • use of a much longer period of historical data (back to 1950).

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More information is given in Documentation and a full description of ERA5ERA-5.

More information regarding differences between ERA-Interim and ERA5ERA-5.


Additional sources of information

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