Simulation of the Martian atmosphere using a CCSR/NIES AGCM

The new simulation of Martian general circulation based on CCSR/NIES AGCM has been performed and the numerical results analyzed. We attempt to reproduce the atmospheric states of Mars which have been observed by the Mars Global Surveyor, and Viking by introducing three kinds of time- and latitude-dependent dust opacity scenarios which are made to be consistent with the past observational results, as the observed dust distribution during spring and summer in south hemisphere varies largely at each year and so does observed atmospheric conditions. The model with TES2 dust scenario, which is the dust distribution based on the observation by the Mars Global Surveyor in 1999, generally reproduces distributions of temperature and zonal wind observed by the Mars Global Surveyor in 1999, though the temperature tends to be lower at high altitude. The maximum value of CO₂ ice thickness at polar regions relatively reproduces the observation, but the edge of the northern and southern seasonal caps are outside of the observational results during spring, which results in lower surface pressure especially in northern spring. Annual variations of the amplitudes of the diurnal and semidiurnal tide are qualitatively comparable between our model with VIK1 dust scenario, which is the dust distribution based on the observation by Viking Orbiter in 1977, and observation by Viking Lander 1 in 1977. The baroclinic waves with consistent periods, wavenumbers and phase speeds with observational results by Viking Lander 2 in 1977 are reproduced in the autumn, though in the winter, during the second dust storm, and in the spring, the phase speeds are faster than observation.