Observations and modeling of the 6-hour tide in the upper mesosphere

This paper presents observations and modeling of the 6-hour tide. Radar observations of horizontal winds at Esrange (68degreesN, 21degreesE) indicate that this tidal periodicity is a consistent part of the diurnal variation and is largest during midwinter. Vertical structure and phase coherence provide strong support that the observed oscillations are tidal. Model simulations generate a tide that has many similarities to the observed tide at Esrange. Diagnostic model tests indicate that the tide is forced primarily by the 6-hour component of solar heating. Globally, the monthly mean simulated tide is dominated by the migrating component except near the poles, although the contribution from nonmigrating modes is not negligible. According to the model both migrating and nonmigrating 6-hour tides have small amplitude in low latitudes.