Rogue vertical drafts in the mesosphere and lower thermosphere: evidence and implications

Observational evidence of extreme vertical velocities ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="m1"> <mml:mrow> <mml:mo stretchy="false">|</mml:mo> <mml:mtext>w</mml:mtext> <mml:mo stretchy="false">|</mml:mo> <mml:mo>≥</mml:mo> <mml:mn>12.5</mml:mn> </mml:mrow> </mml:math> 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 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="m2"> <mml:mrow> <mml:mo>∼</mml:mo> </mml:mrow> </mml:math> 12 days during summer over Northern Norway, assuming a 1,000 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.