This site provides data from the 20th Century Reanalysis Project, offering temperature, pressure, humidity, and wind fields in 200 km sections all around the earth from 1871 to 2012, every 6 hours, based on historical data. The ensemble mean and standard deviation for each value were calculated over a set of 56 analyses and short-term forecasts. Data for each of the 56 ensemble members are included here. The dataset consists of files in netCDF 4 format that are available for download from the National Energy Research Scientific Computing Center.

How to Download the Data

You can browse and download the data by clicking the Browse Data button below. This brings you to the data directories. In the analysis or first_guess directory, you will find a directory for each variable calculated. Click a variable name to see a list of yearly files for that variable. From here, you can click the filename for one of the years (e.g., t850_1871.nc for air temperature at 850 hPa during 1871) to see detailed download options. You can also click the file size in the Download column to begin downloading the entire file over http. When viewing download options, you will see tabs for alternative download tools, such as Ferret, GrADs, IDL, and PyDap. Click a tab for command-line instructions.

get data

As an example, suppose you want to download surface air pressure data for 1871. This is abbreviated as "ps". Click the Browse Data button. Then follow the links to "analysis", then "ps". Click "ps_1871.nc" in the Filename column to get a form for specifying download options. Place a check mark in the box labeled "ps," and enter colon-separated start, step, and stop values for your desired ranges of time, location, and ensemble membership. To include a listing of available times, latitudes, longitudes, or ensemble members for this variable and year, check the corresponding box and enter the start, step, and stop values you'd like. Finally, click "Download data."

You can also grab data from this site using wget. Here's how:

wget http://portal.nersc.gov/pydap/20C_Reanalysis_ensemble/
analysis/{variable}/{variable}_{year}.nc

Here's an example:

wget http://portal.nersc.gov/pydap/20C_Reanalysis_ensemble/
analysis/cape/cape_1901.nc

Daily averages and monthly averages are in the analysis.derived and first_guess.derived directories.

Having trouble opening the data files? See netCDF4 Compatibility Issues.

Articles about the 20th Century Reanalysis Project

ASCR Newsletter:
Reanalysis Project targets once-and-future weather

ESRL Newsletter:
Reconstructing History: Understanding past weather events to improve climate forecasts

SciDAC Review:
Bridging the Gap between Science and Weather

Collaborator Institutions

Cooperative Institute for Research in Environmental Sciences
National Oceanic and Atmospheric Administration
UK Met Office Hadley Centre, Atmospheric Circulation Reconstructions
over the Earth
Full List

Related Links

20th Century Reanalysis Project
Reanalysis Intercomparison and Observations
Atmospheric Circulation Reconstructions over the Earth
Physical Sciences Division, NOAA/ESRL
Cooperative Institute for Research in Environmental Sciences (CIRES)
DOE INCITE Program
National Energy Research Scientific Computing Center (NERSC)
National Center for Computational Sciences (NCCS), Jaguar

Contact

Gilbert P. Compo
CIRES, University of Colorado at Boulder, and Physical Sciences Division, Earth System Research Laboratory, National Oceanic and Atmospheric Administration
gilbert.p.compo at noaa.gov

Acknowledgment

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 the 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."

Reference

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.