MERRA-2 — LLMpedia

MERRA-2
Name	MERRA-2
Provider	National Aeronautics and Space Administration
Program	Global Modeling and Assimilation Office
First release	2015
Spatial resolution	0.5°×0.625°
Temporal resolution	hourly to monthly
Variables	atmospheric composition, aerosols, meteorology

Contents

MERRA-2 is a modern atmospheric reanalysis developed by the National Aeronautics and Space Administration's Global Modeling and Assimilation Office as a successor to earlier reanalyses. It provides a continuous, multidecadal, assimilated dataset integrating observations from satellites and in situ platforms for climate, weather, and atmospheric composition research. MERRA-2 underpins studies across institutions such as the National Oceanic and Atmospheric Administration, European Centre for Medium-Range Weather Forecasts, and academic centers including Massachusetts Institute of Technology and University of Colorado Boulder.

Overview

MERRA-2 extends and refines the legacy of reanalysis efforts that include ERA-Interim, ERA5, NCEP/NCAR Reanalysis, and JRA-55, addressing aerosol and composition cycles to support investigations by groups like NASA Goddard Institute for Space Studies and Jet Propulsion Laboratory. It assimilates retrievals from satellite missions such as MODIS, MISR, CALIPSO, Aqua, and Terra, and incorporates in situ networks like Global Climate Observing System-aligned platforms and radiosonde programs from agencies including World Meteorological Organization members. The project has been cited in work by researchers at Scripps Institution of Oceanography, Columbia University, and University of Oxford.

MERRA-2 delivers gridded fields of atmospheric state variables, reanalysis increments, and aerosol diagnostics used by the Intergovernmental Panel on Climate Change community and regional modeling groups. Product suites support modeling at institutes like Lamont–Doherty Earth Observatory and operational centers such as NOAA/NCEP via coupled analyses for studies at Purdue University and Stanford University. Datasets include hourly instantaneous fields, three-hourly averages, and monthly means consumed by projects at European Space Agency and National Center for Atmospheric Research for trend analysis and model evaluation. Coverage includes profiles, surface fluxes, and aerosol optical depths leveraged by teams at NASA Langley Research Center and University of Maryland.

The assimilation framework builds on the GEOS (Goddard Earth Observing System) model family and uses a 3D/4D-Var–derived incremental analysis scheme developed at the Global Modeling and Assimilation Office. Observational inputs derive from instruments operated by NOAA, EUMETSAT, and Japanese Aerospace Exploration Agency, with radiance assimilation approaches informed by methodologies from European Centre for Medium-Range Weather Forecasts research. Aerosol reanalysis employs the Goddard Chemistry Aerosol Radiation and Transport model and leverages emission inventories curated by groups such as Community Emissions Data System contributors and researchers at Harvard University. The system architecture is implemented on computing resources historically provided by facilities like NASA Advanced Supercomputing and has been coordinated with data centers including National Snow and Ice Data Center.

Validation campaigns compare MERRA-2 outputs with independent records maintained by Global Precipitation Climatology Project, Atmospheric Radiation Measurement, and airborne campaigns from NASA ER-2 and NOAA P-3 missions. Intercomparisons with ERA5 and JRA-55 have been performed by researchers at Princeton University and University of Washington to assess biases in temperature, humidity, and aerosol fields. Studies by teams at Pacific Northwest National Laboratory and Lawrence Livermore National Laboratory quantify improvements in aerosol optical depth and surface radiation relative to predecessor datasets, while diagnostics using measurements from AERONET provide site-level evaluation at observatories operated by CIESIN and university consortia.

MERRA-2 supports climate attribution and air quality work cited by the Intergovernmental Panel on Climate Change and used in policy-related assessments by agencies such as United States Environmental Protection Agency and regional authorities in collaboration with World Health Organization frameworks. It underlies research on aerosol–radiation interactions by groups at California Institute of Technology, studies of extreme events by National Center for Atmospheric Research convened teams, and hydrometeorological investigations by University of California, Irvine and University of Illinois Urbana-Champaign. MERRA-2 products feed into reanalysis-driven ocean forcing used by Scripps Institution of Oceanography and ecosystem impact studies at Cornell University.

Limitations include dependence on input-observation availability from platforms like Aqua and sensitivity to retrieval biases identified by European Space Agency and NOAA assessments; these issues motivate joint efforts with institutions such as Massachusetts Institute of Technology and Imperial College London to refine aerosol emissions and chemistry. Future developments discussed with collaborators at European Centre for Medium-Range Weather Forecasts and NASA Jet Propulsion Laboratory include higher spatial resolution, coupled ocean–atmosphere extensions, and improved assimilation of next-generation sensors from missions led by NASA and JAXA. Continued community validation with consortia including AERONET and Global Climate Observing System will guide upgrades and interoperability with datasets like ERA5 and climate model ensembles used by IPCC working groups.

Category:Reanalysis datasets