Seasonal characteristics of gravity waves in the middle atmosphere over Gadanki using Rayleigh lidar observations

摘要

Extensive study of middle atmospheric gravity waves (GWs) has been carried out to characterize seasonal variability of wave associated potential energy and vertical component of horizontal momentum flux with long term database (1998-2008) over Gadanki (13.5°N, 79.2°E), India. GWs are observed to transport significant energy and momentum flux with considerable variability throughout the seasons. Wave dissipation is found to be quite large (>30%) at upper mesospheric altitude. Dominant annual oscillation (AO) is observed in the energy and momentum flux pattern in the middle atmosphere. Power spectral density of the vertical wavenumber spectra of normalized temperature derived for the upper stratosphere and mesosphere exhibit resemblance in the saturated region. Logarithmic slope of vertical wavenumber spectra reveals more negative value and near to the model estimation in the upper stratosphere (~-2.83) than the mesosphere (~-2.43), which implies linear wave theory can explain stratospheric wave characteristics in a better way than mesospheric characteristics.