SuperDARN Radar Observations of Quasi-Biennial Oscillation in High Latitude Mesospheric Mean Winds Due to Quasi-2-Day Planetary Wave Activity

Abstract:

Backscatter from meteor trails measured by SuperDARN radars in their near-field range gates can be used to study dynamics of the neutral winds at mesospheric altitudes. Several previous studies have used SuperDARN mesospheric wind measurements to study planetary wave activity, tidal activity and long term analysis of mean winds. Here, we focus on examining interannual variability in the mean zonal winds due to Quasi-Biennial Oscillation (QBO) using 13 years of mesospheric wind data collected by two high-latitude SuperDARN radars. Previous studies have reported the easterly phase of the mesospheric winds becomes enhanced after the March equinox during the westerly phase of the stratospheric QBO. However, we find the westerly phases also show a QBO modulation such that there is an increase in late winter westerly winds when the stratospheric QBO is easterly and in the autumn westerly winds when the stratospheric QBO is westerly. This observation coincides with enhanced quasi-2-day planetary wave activity in the upper mesosphere during winter when the QBO is easterly and during autumn when it is westerly. We speculate that filtering of gravity waves through the enhanced 2-day planetary wave activity may be responsible for producing the QBO modulation of the winds in the mesosphere, thereby vertically and latitudinally coupling the equatorial stratospheric winds and high latitude mesospheric winds during late winter and autumn.