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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.


The AMS Journals Special Collection for MERRA-2 has been released.

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.


CERA-20C: ECMWF has released their second reanalysis (and first coupled) of the 20th century. More details here.

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.

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

Pages and Meetings

Last Millennium Reanalysis workshop 2-3 Oct 2017: Discuss the Last Millennium Reanalysis and paleoclimate data assimilation at its third workshop, to be held Oct 2-3 at the National Center for Atmospheric Research (Mesa Lab) in Boulder, CO. Attend a 1-day hackathon on October 4 to provide graduate students and early-career scientists with hands-on training to use the newly available data and code to perform experiments, work with the output, and analyze results. Limited travel support is available, with priority given to junior participants.  Register at  Address questions to Loretta Quinn at UCAR ( 
AGU Session 25961 Progress in Reanalysis: Development, Evaluation, and Application 
AGU Session 25204 Advances in Integrated Observations, Modeling and Predictions for Weather, Climate and Impact Assessments 

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.