The Modern Era Retrospective-analysis for Research and Applications (MERRA) is a NASA atmospheric data reanalysis for the satellite era using a major new version of the Goddard Earth Observing System Data Assimilation System Version 5 (GEOS-5). MERRA focuses on historical analyses of the hydrological cycle on a broad range of weather and climate time scales, and places the NASA EOS suite of observations in a climate context. The MERRA time period covers the modern era of remotely sensed data, from 1979 through the present. MERRA is being conducted with version 5.2.0 of the GEOS-5 ADAS with a 1/2˚ latitude × 2/3˚ longitude ×72 layer model configuration . MERRA also provides both 2D and 3D atmosphere analyses with different time frequency including3-hourly ,6-hourly , daily and monthly .