Numerical Experiment of Radiative-Convective Equilibrium of the Martian Atmosphere

Abstract

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.

Effects of Dust on Radiation Transfer in the Martian Atmosphere (III)

“…2 well. This strong inversion layer at comparatively high altitude at daytime cannot be found in the radiative-convective calculation based on gaseous components alone, in which an inversion layer appears only in the level below a few km in height in the nighttime (e.g., Gierasch and Goody, 1968;Moriyama, 1972).…”

“…From these results we can see the following facts: i) the thermal structure of the Martian atmosphere indicates a very stable feature in dusty atmosphere. A very small convective layer is a marked contrast to the deep and intense convective region in the cases of a pure CO2 or a CO2 and H2O atmosphere (Gierasch and Goody, 1968;Moriyama, 1972). Consequently, temperature is higher than that in dust-free case at upper level; ii) it may safely be said that in dusty case the Martian atmosphere is directly heated up by absorption of solar radiation rather than by heat transport due to convection from the lower layers as in the terrestrial troposphere; iii) the diurnal temperature range in the middle and upper "troposphere" is supposed to be much larger than that for the dust-free cases because of large diurnal heating of atmosphere due to absorption of solar radiation by dust; iv) for the case of a large optical thickness of And two crosses show the ground temperatures for dustfree atmosphere, for (c) and (d).…”

“…Then, intense convective activity during daytime is predicted under the clear condition (Gierasch and Goody, 1968;Moriyama , 1972). This instability of the atmosphere would increase probability of occurence of a Great dust storm than at dusty conditions, i.e., localized dust storms would grow up and a Great dust storm which is seen by ground-based observers would appear.…”