Masatsugu Odaka

A numerical simulation of Martian atmospheric convection with a two-dimensional anelastic model: A case of dust-free Mars

A numerical simulation of convection in the Martian atmosphere driven by surface heating is performed with a two-dimensional anelastic model employing radiative process appropriate for clear sky conditions. The model diurnal surface temperature variation is specified, based on typical observed diurnal variations. The simulated convection extends up to about 10 km and the maximum values of vertical and horizontal wind speeds are about 30 m/sec and 20 m/sec, respectively. The instantaneous values of calculated surface stress frequently exceed the minimum threshold value for raising dust from the surface. These results suggest that kilometer-scale surface stresses associated with convection forced by diurnally-varying surface heating may strongly contribute to dust injection in the Martian atmosphere.

A numerical study of the Martian atmospheric convection with a two-dimensional anelastic model

Thermal convection of the Martian lower atmosphere is examined by the use of a two-dimensional anelastic model with a resolution fine enough to describe convection eddies.For a homogeneous radiative cooling of 50 K/day given in the layer below 5 km, a layer of time-dependent convection develops up to about 6 km in height. The intensity of realized vertical winds ranges up to 20 m/s. The dust, which is injected into the lowest layer and treated as a passive tracer, is transported immediately in the convection layer and mixed uniformly.The intensity of the horizontal winds near the surface reaches about 10 m/s, which, combined with large-scale motions, is expected to contribute to the dust injection into the atmosphere.

A Numerical Study of Convection in a Condensing CO2 Atmosphere under Early Mars-Like Conditions

AbstractCloud convection of a CO2 atmosphere where the major constituent condenses is numerically investigated under a setup idealizing a possible warm atmosphere of early Mars, utilizing a two-dimensional cloud-resolving model forced by a fixed cooling profile as a substitute for a radiative process. The authors compare two cases with different critical saturation ratios as condensation criteria and also examine sensitivity to number mixing ratio of condensed particles given externally.When supersaturation is not necessary for condensation, the entire horizontal domain above the condensation level is continuously covered by clouds irrespective of number mixing ratio of condensed particles. Horizontal-mean cloud mass density decreases exponentially with height. The circulations below and above the condensation level are dominated by dry cellular convection and buoyancy waves, respectively.When 1.35 is adopted as the critical saturation ratio, clouds appear exclusively as intense, short-lived, quasi-period...