Observations of inertia-gravity waves using two radars

The properties of inertia gravity waves have been investigated using the radar data from two sites. A first case study has been carried out over Northern Germany from 17-19 December 1999, using continuous VHF radar measurements with the OSWIN radar at Kuhlungsborn (54.1degreesN, 11.8degreesE). It has been recently shown (Peters et al., 2003), that these waves are generated by an upper tropospheric jet in connection with a poleward Rossby wave breaking event. The diagnostic results basing on a linear theory show a characteristic horizontal wavelength of about 890 km and a vertical wavelength of about 2-3 km in the stratosphere and about 3.3 km in the troposphere. In addition, the spatial structures of these waves are studied with help of the data of the 482 MHz wind profiler at Lindenberg (52.2degreesN, 14.1degreesE), separated by about 300 km from the Kuhlungsborn radar. Based on wavelet transformations of both data sets, the dominant vertical wavelengths for constant times as well as the dominant periods for constant altitudes are comparable. Temporal and spatial differences of the observed waves are discussed using complex cross-spectral analyses of the results of both radars. Finally, we will extend our investigation to a region in the vicinity of the Scandinavian mountain ridge to study the influence of orographically generated mountain waves on inertia-gravity waves generated in the upper troposphere. For selected events we will combine the VHF radar data from two sites at Andenes(69.3degreesN, 16.0degreesE) and Kiruna(67.9degreesN, 21.1degreesE) before and behind the Scandinavian mountain ridge.