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20th Century Reanalysis

Dataset Information and Access | Acknowledgments | References | Analysis and Plotting Pages | Related Links and Datasets | Feedback



Using a state-of-the-art data assimilation system and surface pressure observations, the Twentieth Century Reanalysis Project is generating a six-hourly, four-dimensional global atmospheric dataset spanning 1871 to 2012 to place current atmospheric circulation patterns into a historical perspective.

20th Century Reanalysis and PSD: The NCEP-NCAR Reanalysis product starts from 1948, leaving many important climate events such as 1930's dust bowl droughts uncovered. To expand the coverage of global gridded reanalyses, the 20th Century Reanalysis Project is an effort led by PSD and the CIRES at the University of Colorado to produce a reanalysis dataset spanning the entire twentieth century, assimilating only surface observations of synoptic pressure, monthly sea surface temperature and sea ice distribution. The observations have been assembled through international cooperation under the auspices of the Atmospheric Circulation Reconstructions over the Earth initiative (ACRE), and working groups of GCOS and WCRP. The Project uses an Ensemble Filter data assimilation method which directly yields each six-hourly analysis as the most likely state of the global atmosphere, and also estimates uncertainty in that analysis. This dataset will provide the first estimates of global tropospheric and stratospheric variability spanning 1871 to 2012 at six-hourly resolution (V2). The first version has global coverage spanning 1908-1958, and two degree longitude-latitude horizontal resolution. V1 is available from NCAR.

Recreating the Knickerbocker Storm of 1922: One of the deadliest snowstorms in U.S. history was the Knickerbocker Storm, a slow- moving blizzard that occurred on January 27-29, 1922 in the upper South and Middle Atlantic states. This storm was named after the collapse of the Knickerbocker Theater in Washington, D.C. shortly after 9 p.m. on January 28. The movie theater's flat roof collapsed under the weight of 28 inches of wet snow, bringing down the balcony and a portion of the brick wall and killing 98 people, including a Congressman. An arctic air mass had been in place across the Northeast for several days before the storm, and Washington had been below freezing since the afternoon of January 23. The storm formed over Florida on January 26 and took three days to move up the Eastern Seaboard. Snow reached Washington and Philadelphia by noon on January 28 and continued into the morning of January 29. Winds gusting up to 50 mph created blizzard conditions, and heavy drifting blocked roads for days. Railroad lines between Philadelphia and Washington were covered by at least 36 inches of snow, with drifts as high as 16 feet. Figure above presents data from the 20th Century Reanalysis Project's three- dimensional reanalysis of conditions at 7p.m. on January 28, 1922. With data like this available for the entire 20th century, climate researchers hope to improve their models so that they can more confidently predict regional weather trends for the future.

* Source: SCIDAC Review, Spring, 2008

Examples of 20th Century Reanalysis data on NOAA's Science on a Sphere

The Science on a Sphere project has available 3 animations created using the 20th Century V2 precipitable water data. They are the Galveston hurricane of September 1900, the 1917 La Nina transitioning to the 1918 El Nino and 1902-1903 (where the location of the Discovery ship is marked). Users can view these on a 'Science on a Sphere' exhibit and can download the animations from the Science on a Sphere 20th Century Reanalysis webpage.

Analysis and Plotting Tools

Please use these pages below to plot the 20th Century Reanalysis Version 1 and 2 of the data. Additional tools will be forthcoming.
Clicking on graphics will show full sized images of the example plots. Clicking on the plotting tool descriptions,e.g., 1) Monthly Composites, 2) Monthly/Seasonal Google Earth Interface, 3) Sub-Daily Average Composites, and 4) Monthly/Seasonal Google Earth Interface will show respective plotting tool pages. You can also use the PSD Search and Plot page. This is less flexible but can access all the data. Search for dataset(s) 'NOAA-CIRES 20th Century...'.


Version 2: Maps/Cross-Sections


1919 El Nino: 10m zonal wind Jan-Feb anomalies

Google Earth: The NAO and anomalous winter 850mb zonal winds.

Jan 1 1912 US cold snap)
Monthly CompositesMonthly/Seasonal Google Earth InterfaceDaily Composites

Jan 1900 Monthly Ensemble Spread of 2m Specific Humidity

July Heat Waves in NYC: SLP anomaly

Difference of 20CR and NCEP R1 Zonal Averaged Winds during El Nino
Search for and Plot All Fields Sub-Daily Composites WRIT: Mapping Tool

Version 2: Timeseries


Timeseries of monthly mean 850mb zonal wind 40N,2455W

Timeseries of daily mean 1000mb geopotential height wind 0N,0W
Monthly Mean Time Series Extraction/Plotting pageDaily Time Series Extraction page

Timeseries of precipitation: 20CR vs GPCP 6N-6S; 120E-180E

20Cth V2 Derived Climate Indices
WRIT: Timeseries Comparison Webpage20Cth V2 Derived Climate Indices

Version 2: Other Products


Trajectory Plot for Trinity Nuclear Test

Distribution of Monthly Mean 2m Air Temperature at 40N, 255E
WRIT: Trajectory Web Page20Cth V2 Monthly Mean Products

Vertical Profile Historic US Tri-State Tornado

Air temperature anomaly time by longitude plots
for the tropical Pacific area for 1982-3.
Vertical ProfilesTime by Lat/Lon


Dataset Information and Access:

Data and more information can be found at the following sites

Data Access at PSD

Useful dataset analysis plots can be found here:

Obtain plots of the ensemble means and spreads
example is SLP and 500z, Jan 1 12z 1900


The Twentieth Century Reanalysis Project used resources of the National Energy Research Scientific Computing Center managed by Lawrence Berkeley National Laboratory and of the Oak Ridge Leadership Computing Facility at Oak Ridge National Laboratory, which are supported by the Office of Science of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231 and Contract No. DE-AC05-00OR22725, respectively.

Papers using the Twentieth Century Reanalysis Project dataset are requested to include the following text in their acknowledgments: "Support for the Twentieth Century Reanalysis Project dataset is provided by the U.S. Department of Energy, Office of Science Innovative and Novel Computational Impact on Theory and Experiment (DOE INCITE) program, and Office of Biological and Environmental Research (BER), and by the National Oceanic and Atmospheric Administration Climate Program Office."


  • Compo, G.P., J.S. Whitaker, P.D. Sardeshmukh, N. Matsui, R.J. Allan, X. Yin, B.E. Gleason, R.S. Vose, G. Rutledge, P. Bessemoulin, S. Brönnimann, M. Brunet, R.I. Crouthamel, A.N. Grant, P.Y. Groisman, P.D. Jones, M. Kruk, A.C. Kruger, G.J. Marshall, M. Maugeri, H.Y. Mok, Ø. Nordli, T.F. Ross, R.M. Trigo, X.L. Wang, S.D. Woodruff, and S.J. Worley, 2011: The Twentieth Century Reanalysis Project. Quarterly J. Roy. Meteorol. Soc., 137, 1-28. DOI: 10.1002/qj.776 Free and Open Access.
  • Compo,G.P., J.S. Whitaker, and P.D. Sardeshmukh, 2006: Feasibility of a 100 year reanalysis using only surface pressure data. Bull. Amer. Met. Soc., 87, 175-190.
  • Whitaker, J.S., G.P.Compo, X. Wei, and T.M. Hamill 2004: Reanalysis without radiosondes using ensemble data assimilation. Mon. Wea. Rev., 132, 1190-1200.

Related Data Sources:

Other Useful Webpages:

  • PSD Monthly Climate Indices
    Plot, analyze and obtain various ocean and atmospheric indices including the the North Atlantic Oscillation (NAO), the Arctic Oscillation (AO) the SOI and many others.


We would greatly appreciate feedback on its use; in the classroom, for presentations or for research. Mail to at (