MOUNTAIN WAVES FLUXES ACROSS THE TROPOPAUSE

Using observations from the NSF/NCAR Gulfstream V and U. Wyoming King Air research aircraft in the Terrain-Induced Rotor Experiment, wave properties over the Sierra Nevada are analyzed for six cases with cross-barrier flow. Aircraft altitude measured from differential GPS was used to correct the static pressure and compute the vertical energy flux. Energy and momentum fluxes were compared to those predicted by existing theory.

The Eliassen-Palm linear relation between momentum and energy flux (EF=-U*MF) was verified using the aircraft data. Spatial and spectral techniques are employed to document spatial and temporal wave evolution and associated vertical fluxes. No jump in MF or EF was detected at the tropopause. However, in one case (RF10: April 16, 2006) MF was found to vary as a function of height. The Eliassen-Palm relation stipulates that MF should be independent of height and this vertical variation of MF in RF10 appears to be a violation of existing theory for a steady, upward propagating wave.

In the case of RF10, systematically reversed momentum and energy fluxes were consistently found in the stratosphere above 12km. Reversed stratospheric momentum and energy fluxes were sampled repeatedly flying both upwind and downwind and over the course of the entire flight, indicating a downward propagating wave in the lower stratosphere and seemingly ruling out general unsteadiness. The EQuipartition Ratio (EQR=PE/KE) jumps across the tropopause, indicating partial wave reflection. The horizontal wavelengths of the waves also decrease in the stratosphere, as is expected in this higher stability layer. Spectral techniques also suggest the possible presence of a fluxless trapped wave riding near the tropopause.