Mean winds and tides in the Arctic mesosphere and lower thermosphere

A new meteor radar has been deployed at Esrange (68°N, 21°E) near Kiruna in Sweden. The radar has been used to measure winds and tides in the Arctic mesosphere/lower thermosphere region over the interval August 1999 to July 2000. Conspicuous features of the measured mean winds include a strong shear of up to 5 m s^-1 km^-1 in the summer zonal flow, resulting in eastward flows of in excess of 30 m s^-1 at the upper heights observed (97 km). An equatorward meridional flow is observed in summer and winter, which reaches maximum values of ∼13 m s^-1 in a summer jet. Poleward flow in comparison is weak and only occurs at the equinoxes. The monthly mean and seasonal mean behaviors of the amplitudes and phases of the 12- and 24-hour tides are examined and compared to the Global Scale Wave Model-98. The observations are generally very close to the model predictions for the 24-hour tide and for the 12-hour tide in winter. In other seasons, particularly summer, the observed 12-hour tidal amplitudes are significantly larger than those predicted. In spring and summer the wavelength of the 12-hour tide is significantly larger than that predicted.