Reanalysis
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 (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.
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 feedback into the circulation, uses NASA's observations of stratospheric ozone and temperature (when available), and takes steps towards representing cryogenic processes.
