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

The Venus atmosphere Superrotation (SR) is successfully simulated with the high-resolution (1.25 degrees x 1.25 degrees 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. On Venus, large-scale waves in the atmosphere play a crucial role in maintaining its fast westward-moving atmosphere, known as superrotation (SR). Previous observations suggest that there might be long-term variations in the SR. We simulated the Venusian SR using a high-resolution atmospheric computer model to understand the mechanism behind this phenomenon. The simulation reproduced the variations in SR and the main large-scale waves observed in reality. Among these waves, the one with a 5.65-day period is the strongest wave in the upper clouds of Venus, in addition to the atmospheric thermal tides. In the simulations, the SR always varies with the changes in the 5.65-day wave. This result indicates that the 5.65-day wave significantly influences SR, possibly explaining the long-term variations observed in SR. Rossby-Kelvin instability wave mode and their angular momentum (AM) transport to super-rotation are robust in at least 2 Venus General Circulation Models Long-term quasi-periodic (163-222 days) variations in the superrotation and dominant wave simulated by Venus Planetary Climate Model are close to observations Dynamically conserved AM from circulation, 5.65-day, and 8.5-day waves drives quasi-periodic variations of the local jets