Gravity Wave Activity in the Stratosphere and Mesosphere during Hurricane Sam

Multi-instrument observations of gravity wave (GW) activity during Hurricane Sam (2021) were made using AIRS (Atmospheric Infrared Sounder) satellite data, ERA5 reanalysis, and TIMED/SABER temperature profiles. Two GW extraction methods, vertical high-pass filtering and empirical mode decomposition, were applied to quantify wave-induced temperature perturbations. AIRS brightness temperature perturbations revealed a broad spectrum of GWs with horizontal wavelengths ranging from 132— 410 km. During the hurricane's weakening, the TIMED/SABER data shows a ~13.4 K warming at 65—75km in the mesosphere and a mesopause cooling of ~ 15 K, with associated >50% and >300% relative changes of RMST' and gravity wave potential energy density per unit volume, respectively. A continuous wavelet transform method is used to determine the vertical wavelengths from the TIMED/SABER profiles, revealing dominant wavelengths of ~13 km and altitudes of wave dissipation. ERA5 reanalysis background eastward zonal wind is enhanced in the mesosphere and the meridional wind field from 30—80 km experiences a reversal with the hurricane's passage. Using the ERA5 background state, we derive a theoretical bounding envelope for the wave dynamics. The resulting group velocities and momentum fluxes indicate wave saturation.