Inertia gravity waves in the upper troposphere during the MaCWAVE winter campaign – Part I: Observations with collocated radars

During the MaCWAVE campaign, combined rocket, radiosonde and ground-based measurements have been performed at the Norwegian Andøya Rocket Range (ARR) near Andenes and the Swedish Rocket Range (ESRANGE) near Kiruna in January 2003 to study gravity waves in the vicinity of the Scandinavian mountain ridge. The investigations presented here are mainly based on the evaluation of continuous radar measurements with the ALWIN VHF radar in the upper troposphere/ lower stratosphere at Andenes (69.3◦ N, 16.0◦ E) and the ESRAD VHF radar near Kiruna (67.9◦ N, 21.9◦ E). Both radars are separated by about 260 km. Based on wavelet transformations of both data sets, the strongest activity of inertia gravity waves in the upper troposphere has been detected during the first period from 24– 26 January 2003 with dominant vertical wavelengths of about 4–5 km as well as with dominant observed periods of about 13–14 h for the altitude range between 5 and 8 km under the additional influence of mountain waves. The results show the appearance of dominating inertia gravity waves with characteristic horizontal wavelengths of ∼200 km moving in the opposite direction than the mean background wind. The results show the appearance of dominating inertia gravity waves with intrinsic periods in the order of ∼5 h and with horizontal wavelengths of 200 km, moving in the opposite direction than the mean background wind. From the derived downward energy propagation it is supposed, that these waves are likely generated by a jet streak in the upper troposphere. The parameters of the jet-induced gravity waves have been estimated at both sites separately. The identified gravity waves are coherent at both locations and show higher amplitudes on the east-side of the Scandinavian mountain ridge, as expected by the influence of mountains. Correspondence to: P. Hoffmann ([email protected])