The Venus' Cloud Discontinuity in 2022

TL;DR

This study provides the longest continuous observation of Venus's cloud discontinuity, revealing its persistent properties and potential altitude-dependent manifestation, which enhances understanding of Venus's atmospheric dynamics and superrotation.

Contribution

It offers a pioneering long-term characterization of Venus's cloud discontinuity, tracking its properties over 109 days and analyzing its behavior across different cloud layers.

Findings

Discontinuity tracked for 109 days with consistent properties.

Discontinuity may manifest at the top clouds due to altitude changes.

Properties similar to previous observations in 2016 and 2020.

Abstract

First identified in 2016 by JAXA's Akatsuki mission, the discontinuity/disruption is a recurrent wave observed to propagate during decades at the deeper clouds of Venus (47--56 km above the surface), while its absence at the clouds' top ($\sim$70 km) suggests that it dissipates at the upper clouds and contributes in the maintenance of the puzzling atmospheric superrotation of Venus through wave-mean flow interaction. Taking advantage of the campaign of ground-based observations undertaken in coordination with the Akatsuki mission since December 2021 until July 2022, we aimed to undertake the longest uninterrupted monitoring of the cloud discontinuity up to date to obtain a pioneering long-term characterization of its main properties and better constrain its recurrence and lifetime. The dayside upper, middle and nightside lower clouds were studied with images with suitable filters acquired by Akatsuki/UVI, amateur observers and NASA's IRTF/SpeX, respectively. Hundreds of images were inspected in search of manifestations of the discontinuity events and to measure key properties like its dimensions, orientation or rotation period. We succeeded in tracking the discontinuity at the middle clouds during 109 days without interruption. The discontinuity exhibited properties nearly identical to measurements in 2016 and 2020, with an orientation of $91^{\circ}\pm 8^{\circ}$, length/width of $4100\pm 800$ / $500\pm 100$ km and a rotation period of $5.11\pm 0.09$ days. Ultraviolet images during 13-14 June 2022 suggest that the discontinuity may have manifested at the top of the clouds during $\sim$21 hours as a result of an altitude change in the critical level for this wave due to slower zonal winds.