The ERA5 Global Reanalysis: Preliminary Extension to 1950

Bill Bell (Corresponding author), Hans Hersbach, Adrian Simmons, Paul Berrisford, Per Dahlgren, Andras Horanyi, Joaquın Munoz-Sabater, Julien Nicolas, Raluca Radu, Dinand Schepers, Cornel Soci, Sebastian Villaume, Jean‐Raymond Bidlot, Leopold Haimberger, Jack Woollen, Carlo Buontempo, Jean-Noel Thepaut

Publications: Contribution to journalArticlePeer Reviewed

Abstract

The extension of the ERA5 reanalysis back to 1950 supplements the previously published segment covering 1979 to the present. It features the assimilation of additional conventional observations, as well as improved use of early satellite data. The number of observations assimilated increases from 53,000 per day in early 1950 to 570,000 per day by the end of 1978. Accordingly, the quality of the reanalysis improves throughout the period, generally joining seamlessly with the segment covering 1979 to the present. The fidelity of the extension is illustrated by the accurate depiction of the North Sea storm of 1953, and the events leading to the first discovery of sudden stratospheric warmings in 1952. Time series of ERA5 global surface temperature anomalies show temperatures to be relatively stable from 1950 until the late 1970s, in agreement with the other contemporary full-input reanalysis covering this period and with independent data sets, although there are significant differences in the accuracy of representing specific regions, Europe being well represented in the early period but Australia less so. The variability of ERA5 precipitation from month to month agrees well with observations for all continents, with correlations above 90% for most of Europe and generally in excess of 70% for North America, Asia and Australia. The evolution of upper air temperatures, humidities and winds shows smoothly varying behaviour, including tropospheric warming and stratospheric cooling, modulated by volcanic eruptions. The Quasi-Biennial Oscillation is well represented throughout. Aspects to be improved upon in future reanalyses include the assimilation of tropical cyclone data, the spin-up of soil moisture and stratospheric humidity, and the representation of surface temperatures over Australia.

Original languageEnglish
Pages (from-to)4186-4227
Number of pages42
JournalQuarterly Journal of the Royal Meteorological Society
Volume147
Issue number741
Early online dateSep 2021
DOIs
Publication statusPublished - Oct 2021

Austrian Fields of Science 2012

  • 105206 Meteorology

Keywords

  • CLIMATOLOGY
  • ECMWF
  • ERA5
  • REPRESENTATION
  • SURFACE
  • TEMPERATURE DATA SET
  • UPPER-AIR DATA
  • WARMINGS
  • WIND
  • climate reanalysis
  • data assimilation

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