Observation of Gravity Waves and Turbulence at the Polar Night Jet

Abstract

The polar night jet, i.e., the edge of the polar vortex, maximises in the altitude range of 30 km to 70 km. The polar vortex is known to affect even underlying layers and the weather. The polar night jet shows the highest mean wind speeds observed in the atmosphere and likely plays an important role in multi-step vertical coupling not only from the ground, but also from the upper atmosphere downward.Direct measurements of the polar night jet’s extreme atmospheric motion are rare and limited to a few rocket soundings or locations with dedicated remote sensing techniques. We operate lidar and radar instruments capable of measuring temperatures and winds above northern Norway (ALOMAR, 69°N) and northern Germany (Kühlungsborn, 54°N). The instruments have observed the atmosphere frequently inside and outside the Polar Vortex for more than 10 years.Using lidar measurements of temperatures and winds allows for studying up- and downward-propagating gravity waves in complicated dynamical situations that are often found at the polar vortex edge. Observing simultaneously up- and downward propagating waves may indicate gravity wave breakdown as well as the generation of secondary gravity waves and turbulence. Turbulence is frequently detected using the MAARSY VHF radar. So called Polar Mesosphere Winter Echoes (PMWE) are observed if sufficient ionisation and turbulence exist.We will discuss the relationship between waves, turbulence, and the polar vortex based on lidar and radar observations.