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MERRA-2 const_2d_ctm_Nx: Constant Model Parameters for Usage by CTM 0.625 x 0.5 degree V5.12.4 (M2C0NXCTM) at GES DISC

M2C0NXCTM (or const_2d_ctm_Nx) is a data collection in Modern-Era Retrospective analysis for Research and Applications version 2 (MERRA-2). This collection consists of 2-dimensional constant model parameters for usage by the chemistry transport model (CTM), such as the fraction of lake, land, ice, or ocean within a model grid cell. 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. 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 ( 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 email the question on data access to the GES DISC Help Desk (, or the question on science to the MERRA-2 science team (

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