A case study of the mesospheric 6.5-day wave observed by radar systems

In this paper, analysis of wind data detected by six ground-based radar systems located in equatorial and midlatitude belts shows that a strong mesospheric 6.5-day wave event occurred during April-May 2003. We compared the global distribution of the observed 6.5-day wave event with the theoretical wave structure (Rossby normal mode (s, n) = (1, -2)). Additionally, we investigated several important wave characteristics to understand the mesospheric 6.5-day wave event, i.e., wave period, vertical structure, relationship with background wind, propagating direction, and the zonal wave number. Our results are summarized into three points: (1) the latitudinal structure of the mesospheric 6.5-day wave during April-May 2003 is basically in agreement with the theoretical Rossby mode (s, n) = (1, -2), although the wave amplitude of zonal wind peaked at the subequatorial latitude of Northern Hemisphere but not at the theoretical place, equatorial region; (2) the main wave periods and the altitude distribution of large amplitude of this wave event varied with latitude; (3) the downward propagating wave phases indicated that this wave event originated in the lower atmosphere and propagated upward to the upper region.