Spectral Momentum Flux of Multi-Scale Mountain Wave Events

This presentation will discuss several events of mountain waves (MWs) entering the mesosphere and lower thermosphere (MLT) region during the Deep Propagating Gravity Wave Experiment (DEEPWAVE). During these events, there are multiple scales of MWs present with significant amplitudes. These MWs all dissipate just below the region of the zonal wind reversal in the MLT, a critical level for MWs propagating from lower altitudes [Bossert et al., JGR, 120, 2015]. These large amplitude MWs also have significant momentum flux (MF) associated with them. The presented work will include two parts. One issue in obtaining information about the observed MWs is that they are largely confined to the lower side of the sodium layer below the critical level, where either temperature measurements have high associated errors, or the layer itself is perturbed in one location, providing discontinuous sodium data across an altitude. The first part of this research focuses on techniques used to obtain temperature perturbations from sodium density perturbation amplitudes and mixing ratios. These techniques are validated using the fully compressible "Model for Acoustic and Gravity wave Interactions and Coupling" (MAGIC) [Snively and Pasko, JGR, 113, 2008], with simulations obtained from the DEEPWAVE RF22 event [Heale et al. JGR, 122, 2017]. The second part of this presented work will focus on the spectral MF associated with the MW observations over several different days. Figure 1 shows initial results from this research for two separate events on different days. Figure 1a shows the mixing ratio of the 13 July 2014 MW event, and the corresponding spectral MF calculated from the mixing ratios are shown in Figure 1b. Figure 1c shows the temperature perturbations calculated from density perturbations on 1 July 2014. The corresponding MF calculations are shown in Figure 1d. These MW events demonstrate the varying MW spectra, the associated MF, and the MW dissipation and momentum deposition in altitude which can have significant influences on localized drag on mean winds and global circulation.