The Twentieth Century Reanalysis Project

Journal Article · Sat Jan 01 00:00:00 EST 2011 · Quarterly Journal of the Royal Meteorological Society

DOI:https://doi.org/10.1002/qj.776· OSTI ID:1564728

Compo, G. P.; Whitaker, J. S.; Sardeshmukh, P. D.; Matsui, N.; Allan, R. J.; Yin, X.; Gleason, B. E.; Vose, R. S.; Rutledge, G.; Bessemoulin, P.; Brönnimann, S.; Brunet, M.; Crouthamel, R. I.; Grant, A. N.; Groisman, P. Y.; Jones, P. D.; Kruk, M. C.; Kruger, A. C.; Marshall, G. J.; Maugeri, M. ; Mok, H. Y.; Nordli, Ø.; Ross, T. F.; Trigo, R. M.; Wang, X. L.; Woodruff, S. D.; Worley, S. J.

The Twentieth Century Reanalysis (20CR) project is an international effort to produce a comprehensive global atmospheric circulation dataset spanning the twentieth century, assimilating only surface pressure reports and using observed monthly sea-surface temperature and sea-ice distributions as boundary conditions. It is chiefly motivated by a need to provide an observational dataset with quantified uncertainties for validations of climate model simulations of the twentieth century onall time-scales,with emphasisonthe statistics of daily weather. It uses an Ensemble Kalman Filter data assimilation method with background ‘first guess’ fields supplied by an ensemble of forecasts from a global numerical weather prediction model. This directly yields a global analysis every 6 hours as the most likely state of the atmosphere, and also an uncertainty estimate of that analysis. The 20CR dataset provides the first estimates of global tropospheric variability, and of the dataset’s time-varying quality, from 1871 to the present at 6-hourly temporal and 2° spatial resolutions. Intercomparisons with independent radiosonde data indicate that the reanalyses are generally of high quality. The quality in the extratropical Northern Hemisphere throughout the century is similar to that of current three-day operational NWP forecasts. Intercomparisons over the second half-century of these surface-based reanalyses with other reanalyses that also make use of upper-air and satellite data are equally encouraging. It is anticipated that the 20CR dataset will be a valuable resource to the climate research community for both model validations and diagnostic studies. Some surprising results are already evident. For instance, the long-term trends of indices representing the North Atlantic Oscillation, the tropical Pacific Walker Circulation, and the Pacific–North American pattern are weak or non-existent over the full period of record. The long-term trends of zonally averaged precipitation minus evaporation also differ in character from those in climate model simulations of the twentieth century.

• Research Organization: Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States). Oak Ridge Leadership Computing Facility (OLCF); Univ. of California, Oakland, CA (United States); UT-Battelle LLC/ORNL, Oak Ridge, TN (United States)
• Sponsoring Organization: USDOE Office of Science (SC)
• DOE Contract Number: AC02-05CH11231; AC05-00OR22725
• OSTI ID: 1564728
• Journal Information: Quarterly Journal of the Royal Meteorological Society, Vol. 137, Issue 654; ISSN 0035-9009
• Publisher: Royal Meteorological Society
• Country of Publication: United States
• Language: English

Related Subjects

Meteorology & Atmospheric Sciences