The recent DEEPWAVE field project in New Zealand ran from May 25 to July 28, 2014. Its objectives were to observe, understand and predict the deep propagation of gravity waves from the Troposphere into the Stratosphere, Mesosphere and Thermosphere. In addition to surface, balloon and satellite-borne sensors, the project used two research aircraft with airborne in situ and remote sensors; the NSF/NCAR Gulfstream V (GV) and the German DLR Falcon. In this report, we focus on the 247 legs of low-stratosphere (z=12.1km) flight level data from the GV including flights over the ocean and land.

While stratospheric flights over the ocean rarely showed waves exceeding our detection threshold, flights over the NZ Southern Alps show large waves with the expected mountain wave characteristics of positive vertical energy flux (EFz), negative zonal momentum flux (MFx) and upwind horizontal energy flux. The Eliassen-Palm relation between energy and momentum flux (EFz=-U.MF) is well satisfied. The largest EFz=22W/m2 and MFx=-560mPa.

Statistical analysis of flight level mountain waves in DEEPWAVE (Smith et al., 2016) show three surprising aspects: 1) In some cases, the fluxes can change rapidly under steady environmental conditions; 2) The flux-carrying waves shift (i.e. “downshift” ) from dominant wavelengths of 60- 150km to 20-60km for the strong flux cases; 3) The vertical motion in the low stratosphere is dominated by short wavelengths of 6 to 15 km with little horizontal momentum or vertical energy flux. We discuss whether known non-linear wave generation and propagation processes can explain these three aspects.

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*email: ronald.smith@yale.edu
*Preference: Oral