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Modeling and Assimilation: OVERVIEW

Welcome to the Modeling and Assimilation Data and Information Services Center (MDISC).

Atmospheric, land and ocean observations from satellites, aircrafts, ships, and other sources are grouped, modeled or assimilated into various time scales varying from hourly to multi decadal and processed for visualization and analysis for user community. Assimilated data products are available from the GES DISC.

The Goddard Earth Observing System (GEOS) Data Assimilation System (DAS) is used to generate meteorological data assimilation products in support of NASA instrument teams, NASA's research programs, field campaigns, and as a contribution to U.S. weather and climate research. In addition to near-real-time products, the Global Modeling and Assimilation Office (GMAO) is using version 5 of the GEOS DAS (GEOS-5 DAS) for a retrospective atmospheric analysis for the satellite period (1979 - present).This product, the Modern Era Retrospective-analysis for Research and Applications (MERRA) is available online through the MDISC.

Data Availability and Latency:

MERRA data has a latency of about 2-3 weeks after the completion of a month. So for example to obtain any data from June, it will not be available in the archive until about the 2nd to 3rd week of July.

Sign Up for the MERRA Mailing List

Sign up for the MERRA listserv to receive announcements on the latest data information, tools and services that become available, data announcements from GMAO and more! Contact the GES DISC User Services to be added to the list.

MERRA Science Data and Data Processing Questions

Do you have a question about MERRA? Take a look at the File Specification Document and if that doesn't answer your question, users can contact staff with questions on the data, data processing and science. Send questions to

More data will become available from the GES DISC in the future.


Latest News

The highlighted area of the Sierra Nevada Mountains was used to generate a time-series of snow mass, vital to the water interests in California.
May 30, 2014 - The May 2014 issue of The Giovanni News is online

Lightning and NO2 in Africa, rain and floods in Florida, drought and snow in California

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In 2013, the GES DISC provided more data sets, new tools,  and additional information to NASA Earth science data users around the world. See the article for the highlight corresponding to each picture.
Feb 12, 2014 - GES DISC "Top 10" Highlights for 2013

Achievements, accomplishments, and advances

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The AGU Fall Meeting 2013 will take place in San Francisco, CA, from December 9-13, 2013.
Dec 06, 2013 - GES DISC participates in AGU Fall Meeting 2013

GES DISC staff members are authors or co-authors on 22 presentations

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According to NSF, EarthCube  will “greatly increase the productivity and capability of researchers and educators working at the frontiers of Earth system science.”
Oct 21, 2013 - Staff from the GES DISC participate in NSF EarthCube Workshop

Meeting held at George Mason University in Fairfax, Virginia

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The Alps are a great place to ski, but young skiers may be exposed to excessive ultraviolet radiation, according to research conducted with the aid of the NASA Giovanni system. (Astronaut image of the Bernese Alps courtesy of NASA Visible Earth)
Sep 30, 2013 - Newest additions to Giovanni publications list

73 science journal papers on work utilizing Giovanni appeared from May to August, 2013.

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Last updated: Feb 19, 2014 10:24 AM ET