| Summary: | The second generation zonal atmospheric model ZAM2 is being developed and applied to studies of the potential climatic impact of stratospheric injection of trace species by high altitude aircraft. The model is a two- dimensional general circulation model using a 5 deg latitude grid at nine pressure levels extending into the stratosphere. The effect of terms lost by zonal averaging is simulated by introduction of an eddy transport mechanism in which the eddy diffusion coefficient is a function of internal model variables. ZAM2 strives to model the thermodynamics and hydrology of a moist atmosphere under the influence of solar and long wave radiation, and includes precipitation, cloudiness, convection and surface interactions. The planetary surface is represented as fractionally divided at each latitude band between open ocean, sea ice, and land which may have mountains of various heights. A surface energy balance is maintained allowing heat storage in the land, the build-up and decay of snow cover, and the growth and melting of sea ice. The model uses a fifteen minute time step and may be run for several years without severe penalties in computation time. Model validation includes comparison with climatic data and other modeling efforts as well as sensitivity studies of various modeled processes. Application of this model to the Climatic Impact Assessment Program involves studying the effects of injection of aerosols, reduction in stratospheric ozone heating, and possible perturbations resulting from water vapor injection. (auth)
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