Short period gravity wave momentum fluxes observed in the tropical troposphere, stratosphere and mesosphere

Using long-term data (1998-2008) collected from mesosphere-stratosphere-troposphere (MST) radar and Rayleigh Lidar located at a tropical station, Gadanki (13.5°N, 79.2°E), India, vertical flux of the momentum from troposphere to mesosphere associated with the gravity waves of periods in the range 20 min to 2 h is investigated for the first time. The emphasis is on seasonal variability of mean zonal and meridional momentum fluxes in mesosphere and troposphere and vertical flux of horizontal momentum in the stratosphere. At tropospheric altitudes of 11-16 km large enhancement in flux is noticed during equinoxes. In the lower mesosphere in the altitude region 58-62 km the maximum values of flux (∼2.8 m2/s2) observed are pragmatic in winter and spring. Interestingly, the vertical flux of horizontal momentum estimated from lidar is in the range of those estimated from radar data in the overlap altitude region, though the estimates are from two different techniques. In the mesosphere, large variations with altitude in zonal momentum flux are noticed with a magnitude ∼0-4 m2/s2 in summer. In winter and summer the zonal wind direction is opposite to the momentum flux direction between 73 and 80 km and in equinoxes zonal wind follows the momentum flux. The meridional fluxes in the mesosphere are higher in equinoxes (∼10-12 m2/s2).