Studies of gravity wave dynamics at the polar vortex edge using the Esrange lidar

The Arctic polar vortex is a stable stratospheric cyclone across the northern polar region in winter. It has been shown that the variation in wind speed across the vortex region correlates with local gravity wave activity. It is well known that propagating gravity waves transport momentum from the troposphere to higher altitudes in the Earth's atmosphere. Previous studies have also shown that the vertical wavelengths of orographically excited gravity waves are related to the horizontal background wind in the middle atmosphere. The wind speed maximum at the wandering vortex edge therefore offers an excellent opportunity to further investigate the gravity waves' connection to vortex dynamics. The Esrange lidar located to the east of the Scandinavian mountain range (68° N, 21° E) offers ideal observational capabilities of the local atmospheric temperature conditions at the edge of the polar vortex. We use the ECMWF wind dataset to evaluate the position of the vortex edge relative to the Esrange by calculating the potential vorticity across the northern hemisphere. This analysis is then compared to the gravity wave potential energy density (GWPED) calculated from lidar temperature measurements, ranging from 1996 to 2014 for a total of 1500 hours of winter observations. Our analysis shows how the GWPED at Esrange varies as a function of the vortex edge position.