The aftermath of convective events near Jupiter's fastest prograde jet: implications for clouds, dynamics and vertical wind shear

TL;DR

This study models Jupiter's fastest prograde jet near 24°N to understand how convective plumes influence cloud structures, wave phenomena, and vertical wind shear, revealing a wave-driven mechanism behind observed cloud features and their drift rates.

Contribution

The paper introduces a detailed model of Jupiter's jet region incorporating microphysics, demonstrating the role of upper tropospheric waves in shaping cloud features and constraining vertical wind shear.

Findings

A wave traveling at ~75 m/s influences cloud structures.

Observed chevron-shaped cloud features are linked to this wave.

Vertical wind shear affects cloud feature drift rates.

Abstract

The $24^{\circ}$ N jet borders the North Tropical Belt and North Tropical Zone, and is the fastest prograde jet on Jupiter, reaching speeds above $170$ m/s. In this region, observations have shown several periodic convective plumes, likely from latent heat release from water condensation, which affect the cloud and zonal wind structure of the jet. We model this region with the Explicit Planetary hybrid-Isentropic Coordinate model using its active microphysics scheme to study the phenomenology of water and ammonia clouds within the jet region. On perturbing the atmosphere, we find that an upper tropospheric wave develops that directly influences the cloud structure within the jet. This wave travels at $\sim75$ m/s in our model, and leads to periodic chevron-shaped features in the ammonia cloud deck. These features travel with the wave speed, and are subsequently much slower than the zonal wind at the cloud deck. The cloud structure, and the slower drift rate, were both observed following the convective outbreak in this region in 2016 and 2020. We find that an upper level circulation is responsible for these cloud features in the aftermath of the convective outbursts. The comparatively slower observed drift rates of these features, relative to the wind speed of the jet, provides constraints on the vertical wind shear above the cloud tops, and we suggest that wind velocities determined from cloud tracking should correspond to a different altitude compared to the $680$ hPa pressure level. We also diagnose the convective potential of the atmosphere due to water condensation, and find that it is strongly coupled to the wave.