LAUSR

We present a combination of satellite observation and high-resolution model output to understand monsoon convection as a source of high-latitude mesospheric gravity waves (GWs). The GWs generated over the Northern Hemisphere (NH) monsoon region during the 2007 summer and the role of the winds in focusing these GWs toward the high-latitude middle atmosphere are analyzed using the SABER/TIMED satellite temperature data and the high-resolution NOGAPS-ALPHA model results. In the NH, above the stratosphere, the monsoon GW momentum flux (GWMF) exhibits a poleward tilt that follows the slanted structure of the easterly jet. The correlation coefficients (>0.5) between the time series of NH tropical stratospheric GWMF and the global winds also have a slanted structure that coincide with the easterly jet, confirming the modeling theory that stratospheric monsoon GWs are refracted into the summer easterly jet and can reach the high-latitude mesosphere. Since Polar Mesospheric Clouds (PMCs) are sensitive indicators of changes in the polar summer mesosphere, we compared the time series of tropical stratospheric GWMF to the PMC occurrence frequency (OF) obtained from the CIPS/AIM satellite data, to assess the influence of this wave focusing in the mesosphere. There is a significant positive correlation between the high latitude PMC OF and the tropical stratospheric GWMF suggesting a definite influence of monsoon GWs on the high-latitude mesosphere. The disagreement in correlation at the end of the PMC season is attributed to the enhancement of the quasi 5-day planetary wave dominating over the influence of monsoon GWs on PMCs.