Gravity Wave Activity in the Stratosphere and Mesosphere During Hurricane Sam

Abstract

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 to 410 km. During the hurricane's weakening, the TIMED/SABER data shows a ∼13.4 K warming at 65–75 km in the mesosphere and a mesopause cooling of ∼15 K, with associated >50% and >300% relative changes of 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 to 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 are consistent with wave saturation.