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Abstract Mesopause‐region (87 km) gravity waves (GWs) generated by tropical convection are investigated within the four longitude sectors encompassing Africa, the Indian Ocean, the Intertropical Convergence Zone, and South America during the Dec 2023–Feb 2024 Southern Hemisphere monsoon season. Variances () in the OH Q‐line emission measured by the Atmospheric Waves Experiment (AWE) capture GW activity, and precipitation rates (PR) from the Global Precipitation Measurement (GPM) Mission identify regions of convective activity. The zonal component of GWs comprising the between 10S‐10N primarily propagate eastward. The distributions are latitudinally shifted and more confined in local solar time (LST) compared with those of PR. Mesospheric winds (including tides) appear to induce the latitude‐longitude‐LST variability seen in through critical‐level filtering and Doppler‐shifting of the GWs. These new insights into the variability of the GW spectrum entering the ionosphere‐thermosphere system further our understanding of the dynamical connections between tropospheric and space weather. 

Abstract A remarkable, large‐amplitude, mountain wave (MW) breaking event was observed on the night of 21 June 2014 by ground‐based optical instruments operated on the New Zealand South Island during the Deep Propagating Gravity Wave Experiment (DEEPWAVE). Concurrent measurements of the MW structures, amplitudes, and background environment were made using an Advanced Mesospheric Temperature Mapper, a Rayleigh Lidar, an All‐Sky Imager, and a Fabry‐Perot Interferometer. The MW event was observed primarily in the OH airglow emission layer at an altitude of ~82 km, over an ~2‐hr interval (~10:30–12:30 UT), during strong eastward winds at the OH altitude and above, which weakened with time. The MWs displayed dominant horizontal wavelengths ranging from ~40 to 70 km and temperature perturbation amplitudes as large as ~35 K. The waves were characterized by an unusual, “saw‐tooth” pattern in the larger‐scale temperature field exhibiting narrow cold phases separating much broader warm phases with increasing temperatures toward the east, indicative of strong overturning and instability development. Estimates of the momentum fluxes during this event revealed a distinct periodicity (~25 min) with three well‐defined peaks ranging from ~600 to 800 m²/s², among the largest ever inferred at these altitudes. These results suggest that MW forcing at small horizontal scales (<100 km) can play large roles in the momentum budget of the mesopause region when forcing and propagation conditions allow them to reach mesospheric altitudes with large amplitudes. A detailed analysis of the instability dynamics accompanying this breaking MW event is presented in a companion paper, Fritts et al. (2019,https://doi.org/10.1029/2019jd030899).