ERA-15¶

ECMWF 15-year Reanalysis (ERA-15)

Discontinued

At a glance¶

Note on period: January 1979 to December 1993 (15 years) at ECMWF and NCAR GDEX. The CEDA archive holds "a long time-series (January 1979 - February 1994) of consistent meteorological analyses", i.e. it also includes data to the end of February 1994.

Overview¶

ECMWF's first reanalysis, which re-analysed 1979–1993 with "a special version of their 1995 operational data assimilation system and model" held fixed throughout. It used optimal interpolation (OI) and a T106, 31-level model and, together with the contemporaneous NCEP/NCAR reanalysis, is classed as a first-generation reanalysis. Lessons learned (handling of observation biases, quality-control blacklists and more) were carried into ERA-40.

What changes with the successor¶

ERA-15 → ERA-40¶

The move from the first generation (optimal interpolation, T106L31) to the second (3D-Var, T159L60) extended the record back to 1957 and added direct assimilation of satellite radiances and a coupled ocean-wave model.

Sources: Gibson et al. (1997), ERA Description (ERA-15 Report Series No. 1) · Uppala et al. (2005), The ERA-40 re-analysis, QJRMS · Kållberg et al. (2004), The ERA-40 archive (ERA-40 Project Report Series No. 17) · Uppala (2006), From ERA-15 to ERA-40 and ERA-Interim (ECMWF/GEO Workshop) · NCAR Climate Data Guide — ERA-40 · CEDA ERA-15 parameter tables (17 pressure levels)

Compare the two side by side

Available variables¶

Based on the parameter tables of the ERA-15 data held at CEDA. Names are ECMWF GRIB abbreviations (upper case in the original); current ecCodes shows the same codes as lower-case short names (t, 2t, etc.). The original files are GRIB1.

instantaneous mean accumulated maximum minimum static — instantaneous: value at the time stamp · mean/accumulated/maximum/minimum: over the indicated interval · static: does not change with time

Pressure levels (17)¶

Surface and single level¶

Land surface¶

The full variable list is in the official documentation.

How to get the data¶

• NSF NCAR GDEX — ERA-15 Global Surface Reanalysis (d115000) — Web download (HTTPS) / Globus / subsetting
  • Global 6-hourly surface, near-surface and single-level analyses, about 12 GB. Subsetting and format conversion require an NCAR login.
• NSF NCAR GDEX — ERA-15 Global Upper Air Analyses (d115001) — Web download (HTTPS) / Globus / subsetting
  • Global 6-hourly upper-air (pressure-level) analyses, about 55 GB.
• NSF NCAR GDEX — ERA-15 upper-air analyses at model resolution (d115004) — Web download (HTTPS) / Globus
• CEDA Archive — ERA-15 model data — Web download
  • Requires CEDA registration. The ECMWF ERA products licence applies.

Practical tips¶

• According to ECMWF reports, January 1979 – August 1980 was rerun early in production because of an upper-air humidity error, and June 1990 – October 1992 was rerun because satellite cloud-motion winds (except GMS) had been omitted. If you use an old copy, check that it contains the rerun data.
• Snow is reset by observations in every analysis cycle, so the water budget (precipitation − evaporation − runoff) does not close. The data are not suitable for hydrological budget calculations.
• With only 17 pressure levels (top at 10 hPa) and no direct radiance assimilation, this first-generation product is unsuitable for stratospheric or long-term trend work; use ERA5.

Notices and change history¶

No notices yet.

References for your paper¶

Dataset citation¶

NCAR GDEX surface reanalysis (d115000) — DOI 10.5065/EWRQ-NY89

@misc{era15_d115000,
  author    = {{European Centre for Medium-Range Weather Forecasts}},
  title     = {{ERA-15} Global Surface Reanalysis},
  year      = {1997},
  publisher = {NSF National Center for Atmospheric Research},
  doi       = {10.5065/EWRQ-NY89},
  note      = {Accessed DD MMM YYYY}
}

NCAR GDEX upper-air analyses (d115001) — DOI 10.5065/HS1E-5D24

@misc{era15_d115001,
  author    = {{European Centre for Medium-Range Weather Forecasts}},
  title     = {{ERA-15} Global Upper Air Analyses},
  year      = {1997},
  publisher = {NSF National Center for Atmospheric Research},
  doi       = {10.5065/HS1E-5D24},
  note      = {Accessed DD MMM YYYY}
}

Reference papers¶

ERA-15 technical report (no DOI)

@techreport{gibson1997era15,
  author      = {Gibson, J. K. and K{\aa}llberg, P. and Uppala, S. and Hernandez, A. and Nomura, A. and Serrano, E.},
  title       = {{ERA} Description},
  institution = {European Centre for Medium-Range Weather Forecasts},
  address     = {Reading, UK},
  type        = {ECMWF Re-Analysis Project Report Series},
  number      = {1},
  year        = {1997},
  url         = {https://www.ecmwf.int/en/elibrary/9584-era-description}
}

Acknowledgements¶

Credit ECMWF as the producer and give the DOI or catalogue URL of the archive you actually used (NCAR GDEX or CEDA). For the CEDA copy, use the citation given in the CEDA catalogue record verbatim.

Information on the datasets used in this study was compiled with the help of the Korean Climate Data Navigator (KCDN) (Sim, 2026; https://doi.org/10.5281/zenodo.23300923).

Links¶

• ECMWF ERA-15 dataset page
• ERA-15 technical report (ECMWF eLibrary)
• CEDA ERA-15 parameter tables
• From ERA-15 to ERA-40 and ERA-Interim (Uppala, 2006 ECMWF workshop)