Planetary-Scale Wave Activity in Venus Cloud Layer Simulated by the Venus PCM

Abstract

The Venus atmosphere Superrotation (SR) is successfully simulated with the high-resolution (1.25° × 1.25° in longitude and latitude) runs of the Venus Planetary Climate Model (PCM). The results show a clear spectrum and structure of atmospheric waves, primarily with periods of 5.65 and 8.5 days. The simulation reproduces long-term quasi-periodic oscillation of the zonal wind and primary planetary-scale wave seen in observations. These oscillations occur with a period of 163–222 days, although their existence is still debated in observations. The Rossby waves show similarity in wave characteristics and angular momentum (AM) transport due to Rossby-Kelvin instability by comparing the 5.65-day wave in Venus PCM with the 5.8-day wave simulated by AFES-Venus, another Venus General Circulation Model. Similarities are also evident between the 8.5-day wave in Venus PCM and the 7-day wave obtained in AFES-Venus. The long-term variations in the AM budget indicate that the 5.65-day wave is the dominant factor of the oscillation on the SR, and the 8.5-day wave plays a secondary role. When the 5.65-day wave grows, its AM and heat transport are enhanced and accelerate (decelerate) the lower-cloud equatorial jet (cloud-top mid-latitude jets). Meanwhile, the 8.5-day wave weakens, reducing its deceleration effect on the lower-cloud equator. This further suppresses the meridional gradient of the background wind and weakens instability, leading to the decay of the 5.65-day wave. And vice versa when the 5.65-day wave decays.