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the meteorology of Mars

Student paper—First place winner of The Father James B. Macelwane Annual Award in Meteorology, announced at the Annual Meeting of the AMS, Denver, Colorado, 22 January 1975

Paul W. Greiman

A general overview of what is known about the Martian atmosphere and its effects on the physiography of the surface is presented. The composition of the atmosphere of Mars is examined and some of the fluctuations of atmospheric constituents are discussed and followed by a review of the major geological features and what they imply about the behavior of the atmosphere. The characteristics of the Martian general circulation, the aeolian wind regime, and the global dust storm are described. Theories about the evolution of Mars' atmosphere and the possibility of climatic variation are examined. Project Viking, the major project of Martian research in the next several years, is briefly described.

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James B. Pollack, Conway B. Leovy, Paul W. Greiman, and Yale Mintz

Abstract

A three-layer general circulation model, used to simulate the Martian atmosphere, is described and results are presented. The model assumes a dust-free pure C02 atmosphere and allows for a diurnally- varying convective boundary layer. Smoothed Martian topography and albedo variations are incorporated. The simulation described is for the period near southern winter solstice, season of the Viking landings. The zonally-averaged circulation, mass, heat and momentum balances, and properties of stationary and transient waves are described in some detail, and are compared with results of previous simulations of the Martian general circulation, with related features of the Earth's general circulation, and with observed characteristics of the Martian atmosphere.

The principal conclusions are the following: 1) The simulated zonally-averaged circulation is not very sensitive to differences between this model and the earlier general circulation model of Leovy and Mintz (1969), and compares reasonably well with observations, except for differences attributable to dust and season. 2) The meridional mass flow produced by the seasonal condensation of CO2, in the winter polar region has a major influence on the circulation, but, because of the weak influence of atmospheric heat transport, it is controlled almost entirely by radiation. 3) Quasi-barotropic stationary waves forced kinematically by the topography and resembling topographically-forced terrestrial planetary waves, are generated by the model in the winter hemisphere region of strong eastward flow, while baroclinic stationary waves are thermally forced by topography in the tropics and summer subtropics. 4) Transient baroclinically unstable waves, of somewhat lower dominant wavenumber than those found on the Earth, are generated in winter midlatitudes and their amplitudes, wavenumbers and phase speeds closely agree with what has been deduced from the Viking lander observations.

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