Modeling, Analysis, and Prediction (MAP) Program

Global Modeling Initiative (GMI)

The Global Modeling Initiative (GMI) was initiated under the auspices of the Atmospheric Effects of Aircraft Program (AEAP) in 1995. The goal of GMI is to develop and maintain a state-of-the-art modular 3-D chemistry and transport model (CTM) that can be used for assessment of the impact of various natural and anthropogenic perturbations on atmospheric composition and chemistry, including, but not exclusively, the effect of aircraft. The GMI model also serves as a testbed for model improvements.

GMI has developed a modular chemical-transport model with the ability to incorporate different components and inputs, such as meteorological fields, chemical and microphysical mechanisms, numerical methods, source gas emissions, and other modules representing the different approaches of current models in the scientific community, as well as carry out multiyear assessment simulations. Testing GMI results against observations is a high priority of GMI activities. The goals of the GMI effort are to:

• reduce uncertainties in model results and predictions by understanding the processes that contribute most to the variability of model results, and by evaluation of model results against existing observations of atmospheric compostion;
• understand the coupling between atmospheric composition and climate through coordination with climate models; and
• contribute to the assessment of the anthropogenic perturbations to the Earth system.

At present, the GMI model exists in separate tropospheric, stratospheric, and aerosol versions. Stratospheric simulations ozone trends have been carried out from 1995 to 2030 using the winds from the NASA Finite Volume General Circulation Model (FVGCM) and the NASA Finite Volume Data Assimilation System (FVDAS). Tropospheric simulations have been carried out for 1997 conditions, utilizing winds from DAO, as well as the Middle Atmosphere Community Climate Model (MACCM version 3), and the Goddard Institute for Space Studies (GISS-II′). Sensitivities of a new aerosol model (University of Michigan) to meterorological fields and chemical inputs are being tested in Spring 2004.

Ongoing model development includes: a) merging the tropospheric and stratospheric version, to allow coupled stratospheric-tropospheric simulations, and b) incorporation of aerosol microphysics in both the troposphere and stratosphere.To date, GMI has concentrated on evaluating the variability of simulated atmospheric composition due to incorporation of meterological input from different free running general circulation models and assimilation systems. This effort will be expanded to include studies of the variability due to other model processes.

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