A. Governing equations of the model
A.c. Dust transport The spatial distribution of dust mass mixing ratio is calculated by advection diffusion equation which considers gravitational settling of dust. The dust terminal velocity is calculated as follows (Conrath, 1975). is the density of dust particle, is the radius of dust particle, is atmospheric viscosity, is the mean free path of atmospheric gas at . In this study, we set = 3000 kgm-3, = 1.5×10-5 kgm-1sec-1, = 25 hPa, and = 2.2×10-6 m. The equation (A.19) is applied for each dust particle with different radius. However, the size distribution of dust is not considered here for simplicity and the radius of dust particle is supposed to be equal to the mode radius of dust particle in equation (A.38) which is the size distribution function of dust. It is supposed that the dust injection from the surface to atmosphere occurs when the surface stress exceeds some threshold value. The value of dust flux from the surface is those obtained by wind tunnel experiment (White et al., 1997). The value of critical surface stress is described in Section 4.
A numerical simulation of thermal convection in the Martian lower atmosphere.