A numerical experiment of the Martian atmospheric general circulation was performed by using a spectral three‐level linear‐balance model. We examined effects of topography and of radiative scattering of dust suspended in the Martian atmosphere upon the general circulation. Computations were made for a period corresponding to the equinoctial season for the southern hemisphere. Our results indicate that in the stage of development of a dust storm, topography, when it exists in the dusty field, would have a very important role for intensifying winds and suspending dust particles blown up from the surfaces in such a specified region as the Hellas region and that thermally forced transient waves produced by radiative effect of dust are superposed on the quasistationary disturbances induced by the topography. As a result, large coupled oscillations appear in the atmosphere, especially in the temperature fields, having the predominant components of wave number 1 and 2 which would correlate with diurnal and semidiurnal wave components, respectively.
The equations of infrared radiation transfer are numerically solved for the Martian atmosphere, with consideration of the effect of dust, which absorbs, emits and scatters light. Primary mineral constituent of dust, we assumed, is quartz. Three cases on dust concentration are considered : the first corresponds to a heavy dust storm event, the second to a dusty case and the third to out-of-storm case. From the solutions obtained by the method of an iterative numerical integration, radiative heating or cooling rates in the atmosphere are calculated as a function of height. The computation results show that on Mars, the infrared radiative cooling rates due to dust cannot be overlooked in the lower levels within dusty atmosphere. Especially, at a dust storm event, cooling in the infrared regions would be a very important term as well as heating due to absorption of the incident solar radiation by dust, and the thermal structure of the Martian atmosphere seems to be determined by dust alone. Our result also indicates that even at out-ofstorm events, cooling rate due to dust seems to have the same order as the magnitude of infrared radiative cooling due to CO2.
A three-level linear-balance model for studies of the general circulation using the spectral method is presented with some preliminary results of time integration of the model for a specified terrestrial atmospheric condition.The model is, firstly, integrated for 180 model days under a specified condition to obtain a quasi-steady state without eddies, starting from a calm atmosphere.The zonally symmetric state thus obtained is unstable for the disturbance with zonal wavenumber 5 or 6, according to the linear theory of baroclinic instability. Secondly, after adding disturbances with small amplitudes to the above results of zonally symmetric model, the model integration is continued for another 180 model days to obtain a quasi-steady state with including eddies. The baroclinic instability appears to be released around the day 40, and thereafter the near-equilibrium state is obtained. The results are illustrated mainly for the zonal mean field averaged during either the period of the last 100 days or that of release of baroclinic instability (the day 30-50), and for the time evolutions of energy components and energy conversion terms. The results are not necessarily realistic, because somewhat large values are used tentatively for a part of several parameters, such as the vertical eddy mixing coefficient. Nevertheless, reasonable results are obtained and they are consistent under the model assumption.In order to study extensive problems concerning the general circulation and the climate of the planetary atmospheres, such a numerical model as is simple, economical and easy to handle is useful and worth-while to construct. So far as the preliminary results are concerned, we may say that the present model is one of powerful tools for further studies on the above subjects.
If three assumptions shown in the text are adopted, we can replicate the *18O-derived observations of ice mass evolution. Our results suggest that the large free oscillations with 100 kyr period may be governing the most predominant oscillations in the actual climate, and that the effect of variation in CO2 which would be induced by the link between biological action and the Milankovitch insolation variation would be superposed non-linearly on the free oscillation system with phase lock of the major variation, and play an important role in an apprearance of the real *18O data.
Temperature distributions and its diurnal changes in the Martian atmosphere are computed numerically under a radiative-convective equilibrium. Especially, the green house effect of H2O having the amount obtained by the recent observations, and "dry-ice theory" about the polar cap are investigated. The effects of solar radiation, infrared radiation, sensible heat and conductive heat from the ground are included in this computation. It is assumed that carbon dioxide (83 m-STP) and a small quantity of water vapour (35 micron precipitable water) are the radiating gases in the model atmosphere that has a surface pressure of 6.1 mb. The model atmosphere is divided into 15 layers with height increment of 2 km between the surface and 30 km altitudes. The main results indicate that 1) the green house effect of H2O cannot be neglected at the nighttime near the ground; 2) 'at the nighttime the temperature inversion appears near the ground, and isothermal layer below 6 km except 85°N in summer season; 3) the tropopause-like level may reach 16 km at equatorial equinox, and 10 km 42°S in winter and 85°N in summer. Production rate of solid-CO2 is estimated basing upon the results of temperature structure and change. The main results imply that 4) at the winter edge of the polar cap, the solid-CO2 may be produced in the early morning, and an opinion that the Martian North Polar Cap in summer may be composed of CO2 is not supported.
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