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Description
M2I3NXGAS (or inst3_3d_gas_Nx) is an instantaneous 2-dimensional 3-hourly data collection in Modern-Era Retrospective analysis for Research and Applications version 2 (MERRA-2). This collection consists of assimilation of aerosol optical depth analysis and aerosol optical depth analysis increment. The data field is available every three hour starting from 00:00 UTC, e.g.: 00:00, 03:00, … , 21:00 UTC.
MERRA-2 is the latest version of global atmospheric reanalysis for the satellite era produced by NASA Global Modeling and Assimilation Office (GMAO) using the Goddard Earth Observing System Model (GEOS) version 5.12.4. The dataset covers the period of 1980-present with the latency of ~3 weeks after the end of a month.
Data Reprocessing: Please check “Records of MERRA-2 Data Reprocessing and Service Changes” linked from the “Documentation” tab on this page. Note that a reprocessed data filename is different from the original file.
MERRA-2 Mailing List: Sign up to receive information on reprocessing of data, changing of tools and services, as well as data announcements from GMAO. Contact the GES DISC Help Desk (gsfc-dl-help-disc@mail.nasa.gov) to be added to the list.
Questions: If you have a question, please read "MERRA-2 File Specification Document", “MERRA-2 Data Access – Quick Start Guide”, and FAQs linked from the ”Documentation” tab on this page. If that does not answer your question, you may post your question to the NASA Earthdata Forum (forum.earthdata.nasa.gov) or email the GES DISC Help Desk (gsfc-dl-help-disc@mail.nasa.gov).
Version Description
The GEOS-5 model version used for processing MERRA-2
Product Summary
Platforms
MERRA-2
Instruments
NOT APPLICABLE
Spatial Extent
N: 90S: -90E: 180W: -180
Spatial Resolution
0.625 Decimal Degrees x 0.5 Decimal Degrees
Location
GLOBAL
Coordinate System
CARTESIAN
Granule Spatial Representation
CARTESIAN
Temporal Extent
1980-01-01 to Present
Data Partner
Goddard Earth Sciences Data and Information Services Center (formerly Goddard DAAC), Terrestrial Information Systems Laboratory, Earth Sciences Division, Science and Exploration Directorate, Goddard Space Flight Center, NASA (NASA/GSFC/SED/ESD/TISL/GESDI
Citation is critically important for dataset documentation and discovery. This dataset is openly shared, without restriction, in accordance with the EOSDIS Data Use and Citation Guidance.
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Citation Copied
Global Modeling And Assimilation Office, & Pawson, S. (2015). MERRA-2 inst3_2d_gas_Nx: 2d,3-Hourly,Instantaneous,Single-Level,Assimilation,Aerosol Optical Depth Analysis V5.12.4 [Data set]. NASA Goddard Earth Sciences Data and Information Services Center. https://doi.org/10.5067/HNGA0EWW0R09 Date Accessed: 2026-05-14
Global Modeling And Assimilation Office, and Steven Pawson. “MERRA-2 inst3_2d_gas_Nx: 2d,3-Hourly,Instantaneous,Single-Level,Assimilation,Aerosol Optical Depth Analysis V5.12.4.” NASA Goddard Earth Sciences Data and Information Services Center, 2015. doi:10.5067/HNGA0EWW0R09. Date Accessed: 2026-05-14
Global Modeling And Assimilation Office, and Steven Pawson. MERRA-2 inst3_2d_gas_Nx: 2d,3-Hourly,Instantaneous,Single-Level,Assimilation,Aerosol Optical Depth Analysis V5.12.4. NASA Goddard Earth Sciences Data and Information Services Center, 2015, doi:10.5067/HNGA0EWW0R09. Date Accessed: 2026-05-14
The table below lists the variables contained within a single granule for this
dataset. Variables often contain observed or derived geophysical measurements
collected from a variety of sources, including remote sensing instruments on
satellite and airborne platforms, field campaigns, in situ measurements, and
model outputs. The terms variable, parameter, scientific data set, layer, and band
have been used across NASA’s Earth science disciplines; however, variable is the
designated nomenclature in NASA’s Common Metadata Repository (CMR).
Variable metadata attributes such as Name, Description, Units, Data Type, Fill
Value, Valid Range, and Scale Factor allow users to efficiently process and analyze
the data. The full range of attributes may not be applicable to all variables.
Additional information on variable attributes is typically available in the data,
user guide, and/or other product documentation.
For questions on a specific variable, please use the Earthdata Forum.