Long-term, model-based analyses of multiple datasets using a fixed assimilation system are a major focus in the GMAO. Building on the success of the atmospheric reanalyses conducted with GEOS, current research and development activities are directed at producing a major Earth System Reanalysis, including atmosphere, land, ocean, and ice.


The Modern-Era Retrospective analysis for Research and Applications, Version 2 (MERRA-2) provides data beginning in 1980 and runs a few weeks behind real time. Alongside the meteorological data assimilation using a modern satellite database, MERRA-2 includes an interactive analysis of aerosols that feed back into the circulation, uses NASA's observations of stratospheric ozone and temperature (when available), and takes steps towards representing cryogenic processes.


The Modern-Era Retrospective analysis for Research and Applications (MERRA) dataset was released in 2009. It is based on a version of the GEOS-5 atmospheric data assimilation system that was frozen in 2008. MERRA data span the period 1979 through February 2016 and were produced on a 0.5° × 0.66° grid with 72 layers. MERRA was used to drive stand-alone reanalyses of the land surface (MERRA-Land) and atmospheric aerosols (MERRAero).

NOTE: MERRA production was discontinued with the completion of analyses through February 29, 2016.