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
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
for additional information.
The Twentieth Century Reanalysis Project version 2c 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. Version 2c is a contribution to the
international Atmospheric Circulation Reconstructions over the Earth
initiative. Support for the Twentieth Century Reanalysis Project is
provided by the U.S. Department of Energy Office of Science (BER)
and the NOAA Climate Program Office MAPP program.