Observational evidence of quasi two-day/gravity wave interaction using MF radar

The gravity wave/quasi two-day wave interaction is an example of gravity wave/large-scale flow interaction, a subject of great interest but insufficient understanding. Here we present evidence, from MF radar data, for the quasi two-day wave modulation of gravity wave activity in the summer mesosphere over Urbane, Illinois (40 degrees 10' 10 " N, 88 degrees 09' 36 " W). A composite analysis of two-day wave events, identified using the meridional winds at 84 km, is performed on the four-hour mean winds and four-hour standard deviations about those means, the latter being representative of gravity wave activity. Our results show that quasi two-day variations in the winds modulate gravity wave activity at higher altitudes.