Monthly Mean Values of the Mesospheric Wind Field over Poker Flat, Alaska

Abstract

Monthly-averaged horizontal and vertical mesospheric wind fields have been measured using the Poker Flat Radar at 65°N latitude during 15 months in 1980–81. The horizontal wind fields are reasonably consistent with previous observations and with some of the current theoretical models that take into account enhanced turbulence and eddy transport observed at mesospheric heights. However, the observed vertical wind field has a quasi-sinusoidal seasonal variation with peak values of 25 cm s⁻¹ both downward near summer solstice and upward near winter solstice and is inconsistent with current models of mean circulation in the meridional plane. Because there are no other comparable vertical wind observations, the possibility of error in the vertical wind measurements was carefully considered and rejected. We conclude that the actual mean circulation is more complex than that implied by current models. Possible complicating factors include nonuniform zonal flow, multicellular meridional structure and an enhanced vertical Stokes drift that would arise from strong eddy activity.