Seasonal Cycle of Gravity Wave Potential Energy Densities from Lidar and Satellite Observations at 54° and 69°N
Irina Strelnikova, Marwa Almowafy, Gerd Baumgarten, Kathrin Baumgarten, Manfred Ern, Michael Gerding, Franz‐Josef Lübken
Abstract
Abstract We present gravity wave climatologies based on 7 years (2012–18) of lidar and Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) temperatures and reanalysis data at 54° and 69°N in the altitude range 30–70 km. We use 9452 (5044) h of lidar observations at Kühlungsborn [Arctic Lidar Observatory for Middle Atmosphere Research (ALOMAR)]. Filtering according to vertical wavelength ( λ z < 15 km) or period ( τ < 8 h) is applied. Gravity wave potential energy densities (GWPED) per unit volume ( E pV ) and per unit mass ( E pm ) are derived. GWPED from reanalysis are smaller compared to lidar. The difference increases with altitude in winter and reaches almost two orders of magnitude around 70 km. A seasonal cycle of E pV with maximum values in winter is present at both stations in nearly all lidar and SABER measurements and in reanalysis data. For SABER and for lidar (with λ < 15 km) the winter/summer ratios are a factor of ~2–4, but are significantly smaller for lidar with τ < 8 h. The winter/summer ratios are nearly identical at both stations and are significantly larger for E pm compared to E pV . Lidar and SABER observations show that E pV is larger by a factor of ~2 at Kühlungsborn compared to ALOMAR, independent of season and altitude. Comparison with mean background winds shows that simple scenarios regarding GW filtering, etc., cannot explain the Kühlungsborn–ALOMAR differences. The value of E pV decreases with altitude in nearly all cases. Corresponding E pV -scale heights from lidar are generally larger in winter compared to summer. Above ~55 km, E pV in summer is almost constant with altitude at both stations. The winter–summer difference of E pV scale heights is much smaller or absent in SABER and in reanalysis data.