Investigation of gravity waves in the troposphere and stratosphere based on radiosonde observations at Lauder (45 °S 169 °E) during DEEPWAVE-NZ

Sonja Gisinger* and A. Dörnbrack, B. Ehard, B. Kaifler, N. Kaifler, M. Rapp, M. Garhammer, M. Bramberger, T. Portele, M. Siller
DLR-Institut für Physik der Atmosphäre

The field phase of DEEPWAVE-NZ (DEEP propagating gravity WAVE experiment over New Zealand) took place in June and July 2014 on the South Island of New Zealand. One goal of DEEPWAVE-NZ was to explore the propagation of gravity waves (GWs) excited by the flow across the SI into the middle atmosphere. Airborne measurements with the NSF/NCAR GV and the DLR Falcon research aircraft were complemented with ground-based measurements at various stations on the SI. To provide measurements in the lower atmosphere up to 30 km altitude, radiosondes were launched at Lauder during periods of mountain wave activity. Methods to analyze radiosonde data for GWs are either based on horizontal velocity data or on the derived ascent rate of the balloon. While the first approach is more sensitive to low frequency (inertial) GWs, the latter is more sensitive to medium to high frequency waves. Using both approaches, the characteristics of the gravity waves spectrum in the troposphere and stratosphere during DEEPWAVE-NZ are analyzed. Furthermore, we investigate, whether the Southern Alps trigger inertial mountain waves as documented for the flow over Scandinavia or whether the horizontal wind measurements are dominated by inertial GWs from other sources. First results show that the mean horizontal propagation direction based on Stokes analysis for inertial GWs are found to be towards directions between W and N for the troposphere and between W and S for the stratosphere for most of the IOPs. Rotary spectra show dominant upward wave propagation in the stratosphere for nearly all IOPs suggesting that the source is located at the tropopause or in the troposphere. Intrinsic frequencies determined from the relationship between the kinetic and potential gravity wave energy are close to the inertial

First results show that the mean horizontal propagation direction based on Stokes analysis for inertial GWs are found to be towards directions between W and N for the troposphere and between W and S for the stratosphere for most of the IOPs. Rotary spectra show dominant upward wave propagation in the stratosphere for nearly all IOPs suggesting that the source is located at the tropopause or in the troposphere. Intrinsic frequencies determined from the relationship between the kinetic and potential gravity wave energy are close to the inertial frequency.


*email: sonja.gisinger@dlr.de
*Preference: Oral