Winds From the Visible (513 nm) Images Obtained by the Venus Monitoring Camera Onboard Venus Express

Abstract

Venus is surrounded by a massive atmosphere, which includes a dense 20-km-thick cloud layer. Its upper boundary is located at approximately 70 km altitude in low latitudes and gradually descends to 65 km toward the poles (Titov et al., 2018). The upper haze extends up to ∼90 km. The clouds have a sharp lower boundary at ∼48 km with lower haze stretching down to ∼33 km. In different spectral ranges, solar scattered light effectively forms at different altitudes. Thus, by analyzing the images taken at different wavelengths, one can derive a three-dimensional wind field. An overview of the useful spectral ranges for Venus observations can be found in Peralta et al. ( 2017).The highest contrast of ∼30% is observed in the ultraviolet (UV) images near 365 nm (Esposito, 1980;Pérez-Hoyos, et al., 2018) due to nonuniform distribution of the unknown UV absorber(s) at the cloud tops. In the visible (VIS) and near-infrared (near-IR) ranges, the contrast is significantly lower (∼3%-6%) and is likely formed by opacity variations in the middle cloud.The current knowledge of the Venus atmospheric dynamics has been recently reviewed by Sánchez-Lavega et al. (2017). The global circulation is mainly characterized by westward zonal winds reaching maximum velocity of about 100 m/s at the cloud top (∼70 km) at low-to-middle latitudes. The zonal wind speed decreases both with decreasing altitude and toward the poles. Poleward meridional motions with much smaller velocities of up to 15 m/s were observed at the cloud top. Horinouchi et al. (2018) derived mean winds at the Venus cloud top from two-wavelength UV imaging at 365 and 283 nm by UVI camera on JAXA's Akatsuki orbiter. These results

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

“…In the current work, by comparing Venus GCMs, primarily with AFES‐Venus, we aim to elucidate the general mechanisms by which the Rossby waves, Kelvin waves, thermal tides, and MMC maintain the SR AM balance. Observations show that there are long‐term variations in SR (Horinouchi et al., 2024; Khatuntsev et al., 2013; Khatuntsev, Patsaeva, Titov, et al., 2022; Khatuntsev, Patsaeva, Zasova, et al., 2022; Kouyama et al., 2013; Rossow et al., 1990) and planetary‐scale waves (Imai et al., 2019; Lai & Li, 2023), and in the present work, we focus on how the AM transport by planetary‐scale waves changes during SR variations. In addition, this study also covers how cloud‐top mid‐latitude and lower‐cloud equatorial jets are connected and whether they are associated with planetary‐scale waves.…”