Gravity waves above the northern Atlantic and Europe during streamer events using Aeolus

Abstract. Information about the energy density of gravity waves (GWs) is crucial for improving atmosphere models. So far, most space-based studies report the potential energy, Epot, of GWs, as temperature measurements from satellites are more common. We use Aeolus wind data to derive the kinetic energy density, Ekin, of GWs above the northern Atlantic and Europe. Assuming perfect instrument performance, this would be a lower limit for the kinetic energy density, as Aeolus only measures the horizontal line-of-sight wind. Aeolus, the European Space Agency's (ESA's) fourth Earth Explorer Mission, was the first Doppler wind lidar in space and measured vertical profiles of the horizontal line-of-sight wind from the ground to an altitude of ∼ 20–30 km between 2018 and 2023. With a vertical resolution of 0.25–2 km, Aeolus measurements are in principle well suited for the analysis of GWs. However, the data quality is a challenge for such analyses, as the error in the data is in the range of typical GW amplitudes in the troposphere and stratosphere. In this study, we derive daily resolved time series of Ekin before, during, and after two streamer events above the northern Atlantic and Europe. Streamers are large-scale tongue-like structures of meridionally deflected air masses, which are caused by enhanced planetary wave activity. They are linked to vertical shear of horizontal wind and a pressure system, two possible GW generation mechanisms. We find that there is a temporal coincidence between the enhanced daily averaged Ekin and occurrence of the streamer events, which we identified in total column ozone measurements. The derivation of GW signals based on Aeolus data is possible, however: we collected about 100 profiles to statistically reduce the uncertainty in the daily averaged Ekin. Compared to non-satellite measurements, those daily averaged values are at the upper border.