Momentum Flux Estimates Accompanying Multi-Scale Gravity Waves over Mt. Cook, New Zealand on 13 July 2014 during the DEEPWAVE Campaign

Abstract

Observations performed with a Rayleigh lidar and an Advanced Mesosphere Temperature Mapper aboard the NSF/NCAR Gulfstream V research aircraft on 13 July 2014 during the DEEPWAVE measurement program revealed a large-amplitude, multi-scale gravity wave (GW) environment extending from ~20-90 km on flight tracks over Mt. Cook, New Zealand. Data from four successive flight tracks are employed here to assess the characteristics and variability of the larger- and smaller-scale GWs, including their spatial scales, amplitudes, phase speeds, and momentum fluxes. On each flight, a large-scale mountain wave (MW) having a horizontal wavelength ~200-300 km was observed. Smaller-scale GWs over the island appeared to correlate within the warmer phase of this large-scale MW. This analysis reveals that momentum fluxes accompanying small-scale MWs and propagating GWs significantly exceed those of the large-scale MW and the mean values typical for these altitudes, with maxima for the various small-scale events in the range ~20-105 m2s-2.