Rogue Vertical Drafts in the Mesosphere and Lower Thermosphere: Evidence and Implications

TL;DR

The paper identifies Rogue Vertical Drafts (RVDs) as extreme vertical wind events in the mesosphere and lower thermosphere, with $|w|$ often exceeding $12.5 m s-1$ and sometimes reaching $60 m s-1$. It synthesizes observational evidence from PMSE, radars, lidar, and airglow, and supplements with DNS and DNS-inspired modeling to argue that RVDs are intermittent tail events of the vertical wind distribution. A key contribution is the proposed recurrence rate (about one event every ~12 days in Northern Norway during summer) and the discussion of mechanisms and implications, including potential transport of space dust and biological material, impacts on atmospheric chemistry and E-layer dynamics, and relevance to climate-driven changes in upper-atmosphere dynamics. The authors call for global, high-resolution wind observations and modeling to establish prevalence and mechanisms, linking RVDs to broader questions in astrobiology, space weather, and upper-atmosphere chemistry.

Abstract

Observational evidence of extreme vertical velocities (|w| ge 12.5 m/s and at times greater than 50 m/s) in the mesosphere and lower thermosphere (MLT), has emerged in recent years. We refer to these events as Rogue Vertical Drafts (RVDs). They exceed five standard deviations of observed vertical velocities and appear as paired updraft-downdraft structures in varicose mode. Four-dimensional observations reveal that RVDs are intermittent, recurrent, and unpredictable. On average, they are expected to occur every sim 12 days during summer over Northern Norway, assuming a 1000 s interval. Different instruments may capture only portions of these events, for example, only upward or downward drafts when restricted to a single altitude range. Despite their rarity, their magnitudes and frequency suggest potential impacts on dust-sized matter escaping from planets, natural and anthropogenic space material, and MLT climate and processes. We propose that RVDs are a fundamental yet under-recognized feature of the MLT, underscoring the need for global observations to assess their prevalence and significance.

Figures (2)

• Figure 1: An example of an RVD observed over northern Norway on July 16, 2016. (a) A Altitude-Time-Doppler Intensity plot of PMSE, color-coded with vertical velocities. (b) Spectrogram at 0430 UT showing extreme updraft and downdraft regions. The dashed red lines indicate the 3-sigma values during that season. (c) A horizontal-altitude cut around 0430 UT of PMSE, also color-coded with vertical velocities. Adapted from chau+etal-2021b.
• Figure 2: Distribution of vertical velocities measured by MAARSY in Northern Norway. Adapted from hartisch+etal-2024.