15A.5 ERA5: State-of-the-Art Global Atmospheric Reanalysis at ECMWF

Thursday, 10 January 2019: 4:30 PM
North 121BC (Phoenix Convention Center - West and North Buildings)
Hans Hersbach, ECMWF, Reading, U.K.; and W. Bell, P. Berrisford, D. Dee, A. Horanyi, C. Peubey, R. Radu, P. de Rosnay, J. Munoz Sabater, R. Dragani, D. Schepers, A. J. Simmons, C. Soci, and J. N. Thépaut

At the European Centre for Medium-Range Weather Forecasts (ECMWF), reanalysis is a key contribution to the Copernicus Climate Service (C3S) that is implemented at ECMWF on behalf of the European Commission. This presentation focuses on the latest ECMWF atmospheric reanalysis ERA5, which is available from 1979 via the C3S Climate Data Store and will soon replace the widely used ERA-Interim reanalysis. ERA5 is the fifth generation of ECMWF atmospheric reanalyses of the global climate, which was pioneered with the FGGE reanalyses produced in the 1980s, followed by ERA-15, ERA-40 and most recently ERA-Interim.

Timely updates are provided and consolidated in an official release about two months behind real time, while preliminary updates are available with a latency of less than a week.
A second phase of ERA5, a pre-extension back to 1950, is currently in production and is to be available by the fall of 2019.

ERA5 is based on a recent ECMWF model cycle which uses the 4D-Var assimilation method for the atmosphere, and includes coupling with ocean waves and a land model.
Radiative forcing follows the evolution of greenhouse gases, volcanic eruptions, ozone and aerosols as recommended by CMIP5 and a consistent
reconstruction is used for sea-surface temperature and sea ice.
A number of reprocessed data records are ingested as well as several data sets that have never been re-used before, and ERA5 is able to assimilate the latest instruments.
Bias correction schemes have been extended and improved.

ERA5 is produced at considerably higher resolution than ERA-Interim: hourly analysis fields are available at a horizontal resolution of 31 km on 137 levels in the vertical.
ERA5 data products also include information about uncertainties which is provided by a lower-resolution 10-member 4D-Var ensemble.

A number of new parameters, such as 100-metre wind speed and direction, are available as part of the output. A database containing all ingested observations, together with detailed information about how they are used, is available to users.
In addition, a dedicated ERA5 land component delivers a land-surface product at an enhanced resolution.

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