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ERA-Interim Project, Monthly Means

| DOI: 10.5065/D68050NT

This historical dataset is recommended for ancillary use only and not as a primary research dataset. It has likely been superseded by a newer, improved dataset.


ERA-Interim represents a major undertaking by ECMWF (European Centre for Medium-Range Weather Forecasts) to produce a reanalysis with an improved atmospheric model and assimilation system which replaces those used in ERA-40, particularly for the data-rich 1990s and 2000s, and to be continued as an ECMWF Climate Data Assimilation System (ECDAS) until superseded by a new extended reanalysis. Preliminary runs indicated that several of the inaccuracies exhibited by ERA-40 such as too-strong precipitation over oceans from the early 1990s onwards and a too-strong Brewer-Dobson circulation in the stratosphere, were eliminated or significantly reduced. Production of ERA-Interim, from 1989 onwards, began in summer of 2006. (The period 1979-1988 was prepended in 2011.)

Through systematic increases of computing power, 4-dimensional variational assimilation (4D-Var) became feasible and part of ECMWF operations since 1997, paving the way to base ERA-Interim on 4D-Var (rather than 3D-Var as in ERA-40). Enhanced computing power also allowed horizontal resolution to be increased from T159 (N80, nominally 1.125 degrees for ERA-40) to T255 (N128, nominally 0.703125 degrees), and the latest cycle of the atmospheric model (IFS CY31r1 and CY31r2) to be used, taking advantage of improved model physics. ERA-interim retains the same 60 model levels used for ERA-40 with the highest level being 0.1 hectopascal. In addition, data assimilation of ERA-Interim also benefits from quality control that draws on experience from ERA-40 and JRA-25, variational bias correction of satellite radiance data, and more extensive use of radiances with an improved fast radiative transfer model.

ERA-Interim uses sets of observations and boundary forcing fields acquired for ERA-40 through 2001, and from ECMWF operations thereafter. Noteworthy exceptions include new ERS (European Remote Sensing Satellite) altimeter wave heights, EUMETSAT (European Organisation for the Exploitation of Meteorological Satellites) reprocessed winds and clear-sky radiances, GOME (Global Ozone Monitoring Experiment) ozone data from the Rutherford Appleton Laboratory, and CHAMP (CHAllenging Minisatellite Payload), GRACE (Gravity Recovery and Climate Experiment), and COSMIC (Constellation Observing System for Meteorology, Ionosphere and Climate) GPS radio occultation measurements processed and archived by UCAR (University Corporation for Atmospheric Research).

NCAR's Data Support Section (DSS) is performing and supplying a grid transformed version of ERA-Interim, in which variables originally represented as spectral coefficients or archived on a reduced Gaussian grid are transformed to a regular 512 longitude by 256 latitude N128 Gaussian grid. In addition, DSS is also computing horizontal winds (u-component, v-component) from spectral vorticity and divergence where these are available. Processing of analysis groups and the surface forecast has been completed for January 1979 through December 2012 (inclusive), or at least 34 years, and will continue as ERA-Interim becomes available thereafter. Data is currently available via NCAR's High Performance Storage System (HPSS), or by delayed mode request which transfers files from the HPSS to our web server for internet download, or via direct internet download, or NCAR's GLADE file system.

Temporal Range:
1979-01-01 00:00 +0000 to 2019-09-01 00:00 +0000 (Entire dataset) Period details by dataset product
Usage Restrictions:

Downloading/Accessing data from this dataset implies acceptance of ECMWF's Terms of Use

Air Temperature Albedo Albedo Cloud Frequency
Cloud Liquid Water/Ice Convergence Dew Point Temperature Evaporation
Geopotential Height Gravity Wave Heat Flux Humidity
Hydrostatic Pressure Ice Extent Incoming Solar Radiation Longwave Radiation
Outgoing Longwave Radiation Potential Temperature Precipitation Amount Runoff
Sea Level Pressure Sea Surface Temperature Shortwave Radiation Skin Temperature
Snow Snow Density Snow Depth Snow Melt
Snow/Ice Temperature Snow/Ice Temperature Soil Moisture/Water Content Soil Temperature
Streamfunctions Sunshine Surface Pressure Surface Roughness
Surface Winds Terrain Elevation Total Precipitable Water Tropospheric Ozone
Upper Air Temperature Upper Level Winds Vegetation Cover Vegetation Species
Vertical Wind Velocity/Speed Vorticity Water Vapor Wind Stress
GRIB parameter table: HTML | XML
Vertical Levels:
See the detailed metadata for level information.
Data Types:
Spatial Coverage:
Longitude Range: Westernmost=180W Easternmost=180E
Latitude Range: Southernmost=89.463S Northernmost=89.463N Detailed coverage information
Data Contributors:
European Centre for Medium-Range Weather Forecasts
Berg, L. K., L. D. Riihimaki, Yun Qian, H. Yan, and M. Huang, 2015: The Low-Level Jet over the Southern Great Plains Determined from Observations and Reanalyses and Its Impact on Moisture Transport J.Climate, 28, 6682-6706 (DOI: 10.1002/qj.864).

Palmeiro, F. M., D. Barriopedro, R. García-Herrera, and N. Calvo, 2015: Comparing Sudden Stratospheric Warming Definitions in Reanalysis Data J. Cliamte, 28, 6823-6840 (DOI: 10.1002/qj.864).

Chen, G., T. Iwasaki, H. Qin, and W. Sha, 2014: Evaluation of the Warm-Season Diurnal Variability over East Asia in Recent Reanalyses JRA-55, ERA-Interim, NCEP CFSR, and NASA MERRA J. Climate, 27(14), 5517-5537 (DOI: 10.1002/qj.864).

Lindsay, R., M. Wensnahan, A. Schweiger, and J. Zhang, 2014: Evaluation of Seven Different Atmospheric Reanalysis Products in the Arctic J. Climate, 27(7), 2588-2606 (DOI: 10.1002/qj.864).

Dee, D. P., M. Balmaseda, G. Balsamo, R. Engelen, A. J. Simmons, and J.-N. Thepaut, 2014: Toward a Consistent Reanalysis of the Climate System Bull. Amer. Meteor. Soc., 95(8), 1235-1248 (DOI: 10.1002/qj.864).

Zappa, G., L. Shaffrey, and K. Hodges, 2014: Can Polar Lows be Objectively Identified and Tracked in the ECMWF Operational Analysis and the ERA-Interim Reanalysis?. Mon. Wea. Rev., 142(8), 2596-2608 (DOI: 10.1002/qj.864).

Siam, M. S., M.-E. Demory, and E. A. B. Eltahir, 2013: Hydrological Cycles over the Congo and Upper Blue Nile Basins: Evaluation of General Circulation Model Simulations and Reanalysis Products J. Climate, 26(22), 8881-8894 (DOI: 10.1002/qj.864).

Decker, Mark, Michael A. Brunke, Zhuo Wang, Koichi Sakaguchi, Xubin Zeng, Michael G. Bosilovich, 2012: Evaluation of the Reanalysis Products from GSFC, NCEP, and ECMWF Using Flux Tower Observations J. Climate, 25, 1916-1944 (DOI: 10.1002/qj.864).

Berrisford, P., P. Kallberg, S. Kobayashi, D. Dee, S. Uppala, A. J. Simmons, P. Poli, and H. Sato, 2011: Atmospheric conservation properties in ERA-Interim Quart. J. R. Meteorol. Soc., 137, 1381-1399 (DOI: 10.1002/qj.864).

Trenberth, Kevin E., John T. Fasullo, Jessica Mackaro, 2011: Atmospheric Moisture Transports from Ocean to Land and Global Energy Flows in Reanalyses J. Climate, 24, 4907-4924 (DOI: 10.1002/qj.864).

Dee, D. P., with 35 co-authors, 2011: The ERA-Interim reanalysis: configuration and performance of the data assimilation system Quart. J. R. Meteorol. Soc., 137, 553-597 (DOI: 10.1002/qj.864).

Poli, P., S. B. Healy, and D. P. Dee, 2010: Assimilation of Global Positioning System Radio Occultation data in the ECMWF ERA-Interim reanalysis Quart. J. R. Meteorol. Soc., 136, 1972-1990 (DOI: 10.1002/qj.864).

Simmons, A. J., K. M. Willett, P. D. Jones, P. W. Thorne, and D. P. Dee, 2010: Low-frequency variations in surface atmospheric humidity, temperature and precipitation: Inferences from reanalyses and monthly gridded observational datasets J. Geophys. Res., 115, 1-21 (DOI: 10.1002/qj.864).

Kobayashi, S., M. Matricardi, D. P. Dee, and S. Uppala, 2009: Toward a consistent reanalysis of the upper stratosphere based on radiance measurements from SSU and AMSU-A Quart. J. R. Meteorol. Soc., 135, 2086-2099 (DOI: 10.1002/qj.864).

Dee, D. P., and S. Uppala, 2009: Variational bias correction of satellite radiance data in the ERA-Interim reanalysis Quart. J. R. Meteorol. Soc., 135, 1830-1841 (DOI: 10.1002/qj.864).

Simmons, A, S. Uppala, D. Dee, and S. Kobayashi, 2007: ERA-Interim: New ECMWF reanalysis products from 1989 onwards. Newsletter 110 - Winter 2006/07, ECMWF, 11 pp. (DOI: 10.1002/qj.864)

Total Volume:
171.52 GB (Entire dataset) Volume details by dataset product
Data Formats:
Related RDA Datasets:
ERA40 T106 6-hourly Surface Analysis and Surface Forecast Fields, created at NCAR
ERA40 T106 Analysis Fields on Pressure Surfaces, created at NCAR
ERA40 T106 Analysis Fields on Model Levels, created at NCAR
Japanese 25-year Reanalysis Project
Japanese 25-year Reanalysis Project, Monthly Means
ERA-20C Project (ECMWF Atmospheric Reanalysis of the 20th Century)
ERA-Interim Project
ERA-Interim Project, Single Parameter 6-Hourly Surface Analysis and Surface Forecast Time Series
JRA-55: Japanese 55-year Reanalysis, Daily 3-Hourly and 6-Hourly Data
JRA-55: Japanese 55-year Reanalysis, Monthly Means and Variances
Metadata Record:
Data License:
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