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JOURNAL OF GEOPHYSICAL RESEARCH,
VOL. 107,
4087,
14 PP., 2002
doi:10.1029/2001JD000479
Extended Canadian Middle Atmosphere Model: Zonal-mean climatology and physical parameterizations
Earth and Atmospheric Sciences Department, York University, Toronto, Ontario, Canada
Department of Physics, University of New Brunswick, Fredericton, New Brunswick, Canada
Earth and Atmospheric Sciences Department, York University, Toronto, Ontario, Canada
Department of Physics, University of Toronto, Toronto, Ontario, Canada
Earth and Atmospheric Sciences Department, York University, Toronto, Ontario, Canada
CCCma, Meteorological Service of Canada, Victoria, British Columbia, Canada
Department of Physics, University of Toronto, Toronto, Ontario, Canada
This paper describes the energetics and zonal-mean state of the upward extension of the Canadian Middle Atmosphere Model, which extends from the ground to ∼210 km. The model includes realistic parameterizations of the major physical processes from the ground up to the lower thermosphere and exhibits a broad spectrum of geophysical variability. The rationale for the extended model is to examine the nature of the physical and dynamical processes in the mesosphere/lower thermosphere (MLT) region without the artificial effects of an imposed sponge layer which can modify the circulation in an unrealistic manner. The zonal-mean distributions of temperature and zonal wind are found to be in reasonable agreement with observations in most parts of the model domain below ∼150 km. Analysis of the global-average energy and momentum budgets reveals a balance between solar extreme ultraviolet heating and molecular diffusion and a thermally direct viscous meridional circulation above 130 km, with the viscosity coming from molecular diffusion and ion drag. Below 70 km, radiative equilibrium prevails in the global mean. In the MLT region between ∼70 and 120 km, many processes contribute to the global energy budget. At solstice, there is a thermally indirect meridional circulation driven mainly by parameterized nonorographic gravity-wave drag. This circulation provides a net global cooling of up to 25 K d−1.
Published 22 May 2002.
Citation: (2002), Extended Canadian Middle Atmosphere Model: Zonal-mean climatology and physical parameterizations, J. Geophys. Res., 107(D10), 4087, doi:10.1029/2001JD000479.
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