A comparison of mean winds and gravity wave activity in the northern and southern polar MLT

Mean winds and waves observed in the mesosphere and lower thermosphere with MF radars located at Davis (69 degreesS, 78 degreesE) and Poker Flat (65 d egreesN, 147 degreesW) are compared. Measurements covering the period from 1999 to mid 2000 show differences in the strength of the horizontal wind fi elds. In the southern hemisphere the zonal and meridional winds reach their maximum values near the summer solstice, but are delayed by 2-3 weeks in t he northern hemisphere. Gravity wave variances also show significant differ ences, as do the strength of vertical velocities.