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Submitted by esrl_admin on Fri, 06/18/2010 - 13:55


Reanalysis is a scientific method for developing a comprehensive record of how weather and climate are changing over time. In it, observations and a numerical model that simulates one or more aspects of the Earth system are combined objectively to generate a synthesized estimate of the state of the system. A reanalysis typically extends over several decades or longer, and covers the entire globe from the Earth’s surface to well above the stratosphere. Reanalysis products are used extensively in climate research and services, including for monitoring and comparing current climate conditions with those of the past, identifying the causes of climate variations and change, and preparing climate predictions. Information derived from reanalyses is also being used increasingly in commercial and business applications in sectors such as energy, agriculture, water resources, and insurance.


Using a collaborative Wiki framework, the goal of is to facilitate comparison between reanalysis and observational datasets. Evaluative content provided by reanalysis developers, observationalists, and users; and links to detailed data descriptions, data access methods, analysis and plotting tools, and dataset references are available. Discussions of the recovery of observations to improve reanalyses is also a focus. The wiki framework encourages scientific discussion between members of and other reanalysis users. 


Save the date! The 5th International Reanalysis Conference (ICR5) will be held 13-17 November 2017.

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Recently published: Introduction to the SPARC Reanalysis Intercomparison Project (S-RIP) and overview of the reanalysis systems 

Kalnay et al. (1996), The NCEP/NCAR 40-year Reanalysis Project, in 20 years since publication has been cited more than 21000 times, as determined from Google Scholar.

A COST/CLIVAR Workshop on Ocean Reanalyses and Intercomparison (ORA-IP) will be held in Toulouse 29-30 June 2017. More info at


MERRA-2: NASA GMAO has just released a new version of the MERRA dataset spanning 1980 to present. More details here.

20CRv2c: NOAA and CIRES just released an improved version of the 20th Century Reanalysis, "2c", spanning 1851-2012, with experimental extension to 2014. More details here.

JRA-55: The new Japanese 55-year Reanalysis (1958 to present) is available from multiple data providers.

ERA-20C: ECMWF just released their first reanalysis of the 20th century. More details here.

CHOR: CMCC just released their first historical ocean reanalyses of the 20th century. More details here.

Pages and Meetings

Area for Questions, Notes, and Comments on recently released Atmospheric Reanalyses: Ask a Question

Extratropical deep cyclones show an increase over the past half century. Discussion Page. Wang et al. (2016) paper.

Surface Solar Radiation in North America from reanalyses and observations. Discussion Page. Slater (2016) Paper.