Numerical Simulation of the Atmospheric Circulation and Climate of Mars

Conway Leovy The RAND Corporation, Sania Monica, Calif.

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Yale Mintz Dept. of Meteorology, University of California, Los Angeles

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Abstract

The Mintz-Arakawa two-level model for planetary atmospheres has been adapted to simulate the atmospheric circulation and climate of Mars. The model uses the primitive equations of atmospheric motion, with heating and cooling by solar and infrared radiative transfer and by turbulent convection. Carbon dioxide is the principal atmospheric constituent and is allowed to condense on the planet's surface, releasing latent heat where the surface cools to the CO2 frost point. Two numerical experiments are made; one simulates orbital conditions at the southern summer (northern winter) solstice of Mars, and the other orbital conditions at the southern autumnal equinox.

The results of the solstice experiment show strong zonal mean west winds in the middle and high latitudes of the winter hemisphere produced by the net eastward Coriolis torque that accompanies the poleward mass transfer toward the condensing CO2 polar ice cap, wave cyclones in the winter hemisphere, a strong ther-mally-direct mean meridional circulation across the equator, with a strong east wind maximum near the equator, and weak east winds over most of the summer hemisphere.

The results of the equinox experiment are more like conditions in the earth's atmosphere. In both hemispheres there are zonal mean west winds in the middle latitudes with wave cyclones in the middle and higher latitudes and east winds in the tropics.

In both experiments there are large diurnal tidal components of the circulation.

Abstract

The Mintz-Arakawa two-level model for planetary atmospheres has been adapted to simulate the atmospheric circulation and climate of Mars. The model uses the primitive equations of atmospheric motion, with heating and cooling by solar and infrared radiative transfer and by turbulent convection. Carbon dioxide is the principal atmospheric constituent and is allowed to condense on the planet's surface, releasing latent heat where the surface cools to the CO2 frost point. Two numerical experiments are made; one simulates orbital conditions at the southern summer (northern winter) solstice of Mars, and the other orbital conditions at the southern autumnal equinox.

The results of the solstice experiment show strong zonal mean west winds in the middle and high latitudes of the winter hemisphere produced by the net eastward Coriolis torque that accompanies the poleward mass transfer toward the condensing CO2 polar ice cap, wave cyclones in the winter hemisphere, a strong ther-mally-direct mean meridional circulation across the equator, with a strong east wind maximum near the equator, and weak east winds over most of the summer hemisphere.

The results of the equinox experiment are more like conditions in the earth's atmosphere. In both hemispheres there are zonal mean west winds in the middle latitudes with wave cyclones in the middle and higher latitudes and east winds in the tropics.

In both experiments there are large diurnal tidal components of the circulation.

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