The Twentieth Century Reanalysis Project, produced by the Earth System Research Laboratory Physical Sciences Division from NOAA and the University of Colorado Cooperative Institute for Research in Environmental Sciences using resources from Department of Energy supercomputers, is an effort to produce a global reanalysis dataset spanning a portion of the nineteenth century and the entire twentieth century (1836 - 2015), assimilating only surface observations of synoptic pressure into an 80-member ensemble of estimates of the Earth system. Boundary conditions of pentad sea surface temperature and monthly sea ice concentration and time-varying solar, volcanic, and carbon dioxide radiative forcings are prescribed. Products include 3 and 6-hourly ensemble mean and spread analysis fields and 6-hourly ensemble mean and spread forecast (first guess) fields on a global Gaussian T254 grid. Fields are accessible in yearly time series (1 file per parameter). The NOAA-CIRES-DOE Twentieth Century Reanalysis Version 3 uses the NCEP Global Forecast Model that was operational in autumn 2017, with differences as described in (Slivinski et al. 2019). Sea ice boundary conditions are specified from HadISST 2.3 (Slivinski et al. 2019). Sea surface temperature fields prior to 1981 are prescribed from the 8-member ensemble of pentad Simple Ocean Data Assimilation with sparse input (SODAsi.3, Giese et al. 2016) and from the 8-member ensemble of pentad HadISST 2.2 for 1981 to 2015. Observations from ISPD version 4.7 are assimilated using an ensemble Kalman filter. The Twentieth Century Reanalysis Project version 3 used resources of the National Energy Research Scientific Computing Center managed by Lawrence Berkeley National Laboratory, which is supported by the Office of Science of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231 and used resources of NOAA's Remote Deployed High Performance Computing Systems. Version 3 is a contribution to the international Atmospheric...

The Twentieth Century Reanalysis Project, produced by the Earth System Research Laboratory Physical Sciences Division from NOAA and the University of Colorado Cooperative Institute for Research in Environmental Sciences, is an effort to produce a global reanalysis dataset spanning a portion of the nineteenth century and the entire twentieth century (1851 - near present), assimilating only surface observations of synoptic pressure. Boundary conditions of pentad sea surface temperature and monthly sea ice concentration and time-varying solar, volcanic, and carbon dioxide radiative forcings are prescribed. Products include 6-hourly ensemble mean and spread analysis fields on a 2 by 2 degree global latitude-longitude grid, and 3 and 6-hourly ensemble mean and spread forecast (first guess) fields on a global Gaussian T62 grid. Fields are accessible in yearly time series (1 file per parameter) and monthly synoptic time (all parameters per synoptic hour) files. This dataset provides the first estimates of global tropospheric variability spanning 1851 to 2012 at six-hourly resolution. Fields from 1851 to 1860 are a first attempt at this period and will be improved in future versions. Fields from 1861 to 2011 are most relevant for climate and weather studies. 20th Century Reanalysis Version 2c uses the same model as version 2 with new sea ice boundary conditions from the COBE-SST2 (Hirahara et al. 2014), new pentad Simple Ocean Data Assimilation with sparse input (SODAsi.2, Giese et al. 2015) sea surface temperature fields from through 2012, Daily High-Resolution-Blended Analyses for Sea Surface Temperature starting with 2013, and additional observations from ISPD version 3.2.9. A low pressure bias in marine pressures from the US Maury Collection (Woodruff et al. 2005, Wallbrink et al. 2009, ) appears to have affected the resultant 20CR version 2c mass-related fields (e.g., pressure, geopotential height) from 1851 to about 1865. Please see opportunities for improvement...

The Twentieth Century Reanalysis Project, supported by the Earth System Research Laboratory Physical Sciences Division from NOAA and the University of Colorado CIRES Climate Diagnostics Center, is an effort to produce a global reanalysis dataset spanning the entire twentieth century, assimilating only surface observations of synoptic pressure, monthly sea surface temperature and sea ice distribution (Version 1 only includes the years 1908 to 1958). Products include 6-hourly ensemble mean and spread analysis fields on a 2 by 2 degree global latitude-longitude grid, and 3 and 6-hourly ensemble mean and spread forecast (first guess) fields on a global Gaussian T62 grid. Fields are accessible in yearly time series files (1 file per parameter) or monthly synoptic files (all parameters included in each file).

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.

Note: Version 2c of this reanalysis (running from 1851 - 2011) is the recommended research version. Please see ds131.2 to access Version 2c.