Airglow Measurements of Mesospheric Wave Structures and Thermal Gradient Variability over a Low-Latitude Indian Station

Simultaneous mesospheric OH and O₂ temperature estimates are used in the present study to characterize the wave perturbations over Gadanki (13.5°N, 79.2°E), a low-latitude station in India. The 65° zenith angle scanning measurements show large variations from one direction to another. The zonal and vertical wavelengths of the observed wave perturbation are found to vary from 740 to 4500 km and 26 to 38 km. The temperature gradient between OH and O₂ layers has been calculated, which shows significant short-period variability. The temperature gradient measurements show large changes from one direction to another. The occurrence of such large temperature gradients within 400 km suggests thermal state of the upper mesosphere to be highly dynamic, which can severely impact the upward propagation of shortperiod gravity waves.