Observations of mesospheric neutral wind 12-hour wave in the Northern Polar Cap

Combined three-station neutral wind observations from 70° to 80°N are used to study the 12-h oscillation from 87 to 130 km altitude. A strong 12-h wave with a 37 km vertical wavelength was observed at Tromsø (69.6°N). The observed phases and vertical wavelength are consistent with the predictions of the Global Scale Wave Model-98 (GSWM-98) for the westward zonal wavenumber two semi-diurnal migrating tide (SDW2). However, the observed amplitudes are much greater than the model prediction at Tromsø. At Resolute (74.9°N), the observed 12-h oscillation in neutral winds appears to be have large contribution from the SDW2, based on the zonal phase shift from Tromsø to Resolute. At Eureka (81.1°N), the 12-h oscillation (not the strongest wave) does not have the predicted phase shift from Tromsø based on the zonal wavenumber of the SDW2. The amplitudes of the 12-h oscillation at Resolute and Eureka are much smaller than those predicted by the GSWM-98 for the SDW2. We believe that the contribution from non-migrating semi-diurnal tide (perhaps, the zonal wavenumber one SDW1) is the likely cause of the inconsistency between the observed and predicted SDW2 in phases and amplitudes at high latitudes.