A report on radar observations of 5-8-day waves in the equatorial MLT region

Abstract

The MF and Meteor radar observations of horizontal winds over Koto Tabang (0.2.DEG.S, 100.3.DEG.E), Pontianak (0.DEG., 109.3.DEG.E), and Pameungpeuk (7.5.DEG.S, 107.5.DEG.E) are utilized to study the characteristics of 5-8-day waves in the mesosphere and lower thermosphere (MLT) region over Indonesia. The wave activity is larger in zonal wind than in meridional wind and in the year 2003, it maximizes before and after northern hemispheric spring equinox. In the year 2004, the wave activity in zonal wind is larger during June-August 2004. During this period, the phase of the wave over Pontianak leads that over Koto Tabang, indicating that the wave is westward propagating with zonal wave number 1. The wave period ranges from 6.3 to 7.0 days over the equatorial sites Koto Tabang and Pontianak, whereas over the southern hemispheric site, Pameungpeuk, it is in the range 6.2-6.4 days. This shows that the dominant period of the wave changes with latitude. The amplitude and phase structures of the wave with altitude are similar among the three sites considered. The wave dominates the MLT dynamics over Pameungpeuk even during second half of CPEA (Coupling Processes in the Equatorial Atmosphere) campaign period (10 April-9 May 2004) with similar dominant wave period near 6.4-days. The wave amplitude is larger during last quarter of the campaign period.