Development of the Grid-Independent GEOS-Chem Module and its deployment in the GEOS-5 General Circulation Model

The Harvard University GEOS-Chem 3-D chemical transport model simulates atmospheric composition - including tropospheric oxidants, primary and secondary aerosols, carbon gases, mercury, and others - driven by NASA's Goddard Earth Observing System (GEOS) assimilated meteorological data. A collaborative project between Harvard University and NASA's Global Modeling and Assimilation Office (GMAO) is focused on redesigning GEOS-Chem's core program structure to meet requirements of the Earth System Modeling Framework (ESMF). This new module, the Grid-Independent GEOS-Chem (GIGC), is capable of operating on an arbitrary horizontal geophysical grid, and has been embedded as the tropospheric chemistry component in GEOS-5, which is an HPC-capable Earth System Model. The primary goals of the GIGC are (1) the use of the GEOS-Chem inside the GEOS-5 Data Assimilation System, for multi-constituent chemical data assimilation of satellite observations (including tropospheric ozone, CO, and NO2); and (2) studies of fully-coupled atmospheric chemistry-climate feedbacks. Both of these goals are enhanced by the ease-of-implementation of new science within GEOS-Chem, which permits model development by GEOS-Chem's wide user community to be quickly integrated within both the stand-alone and the GCM-embedded model versions. Here, we present the first results of the GIGC-coupled GEOS-5 GCM, run at multiple grid resolutions and both rectilinear and cubed-sphere grids. Case studies are used to illustrate model performance at a variety of spatial resolutions.