Blocky Markings and Planetary-Scale Waves in the Equatorial Cloud Layer of Venus

Abstract

Linear and nonlinear behaviors of Venus?s planetary-scale waves are examined by using the two-dimensional model in the equatorial longitude?height plane. The zonal wave 1 gravity waves with phase velocities of 79 and 131 m s?1 are predominant at the cloud base and top, respectively, under the conditions that the waves are forced at the atmospheric bottom. These two waves may contribute to the superrotation in the cloud layer. Nonlinear effects of the planetary-scale 5.57-day wave (with the velocity of 79 m s?1) are likely to appear in the low-stability layer (between 50 and 60 km) before the wave reaches the critical level (63 km). The 5.57-day wave with large amplitude is broken into a few blocks in the low-stability layer, because convective motions are induced by phase structure of the planetary-scale wave?s temperature. Blocky markings in near-infrared observation may be associated with the breaking of the planetary-scale 5.57-day wave. When the forcing is increased, the vertically traveling waves with small scales appear above the low-stability layer. Dynamical interaction between the critical level and the low-stability layer influences the formation of cloud patterns and the redistribution of angular momentum.