Global Modeling Initiative assessment model: Model description, integration, and testing of the transport shell

We describe the three-dimensional global stratospheric chemistry model deve loped under the NASA Global Modeling Initiative (GMI) to assess the possibl e environmental consequences from the emissions of a fleet of proposed high -speed civil transport aircraft. This model was developed through a unique collaboration of the members of the CMI team. Team members provided computa tional modules representing various physical and chemical processes, and an alysis of simulation results through extensive comparison to observation. T he team members' modules were integrated within a computational framework t hat allowed transportability and simulations on massively parallel computer s. A unique aspect of this model framework is the ability to interchange an d intercompare different submodules to assess the sensitivity of numerical algorithms and model assumptions to simulation results. In this paper, we d iscuss the important attributes of the GMI effort and describe the CMI mode l computational framework and the numerical modules representing physical a nd chemical processes. As an application of the concept, we illustrate an a nalysis of the impact of advection algorithms on the dispersion of a NOy-li ke source in the stratosphere which mimics that of a fleet of commercial su personic transports thigh-speed civil transport (HSCT)) flying between 17 a nd 20 km.