TERRAPUB Earth, Planets and Space

Earth Planets Space, Vol. 51 (Nos. 7, 8), pp. 579-592, 1999

Coordinated radar observations of atmospheric diurnal tides in equatorial regions

Toshitaka Tsuda1, Kazunori Ohnishi1, Fusako Isoda1, Takuji Nakamura1, Robert A. Vincent2, Iain M. Reid2, Sri Woro B. Harijono3, Tien Sribimawati3, Agus Nuryanto4, and Harsono Wiryosumarto4

1Radio Atmospheric Science Center (RASC), Kyoto University, Uji, Kyoto 611-0011, Japan
2Department of Physics and Mathematics, University of Adelaide, Adelaide 5005, Australia
3Agency for the Assessment and Application of Technology (BPPT), Jl. M. H. Thamrin No. 8, Jakarta 10340, Indonesia
4Indonesian National Institute of Aeronautics and Space (LAPAN), Jl. Pemuda Persil No. 1, Jakarta Timur 13220, Indonesia

(Received August 16, 1998; Revised June 9, 1999; Accepted June 9, 1999)

Abstract: The long-term behavior of atmospheric tides in the mesosphere and lower thermosphere has been observed with the meteor wind radar (MWR) in Jakarta, Indonesia (6°S, 107°E) from November 1992 to August 1997. The amplitudes and phases of the diurnal tides show systematic seasonal variations, particularly distinct in the meridional component. In addition, substantial interannual variability is evident, characterized by a biennial periodicity of tidal parameters, and considerably small tidal amplitudes exclusively seen in 1996. The MWR results are compared with the Global Scale Wave Model (GSWM) as well as MF radar data collected in two equatorial sites in Pontianak (0.03°N, 109°E) and Christmas Island (2°N, 158°W) for November 1995-July 1997 and January 1996-October 1997, respectively. Comparison studies of these radar data have revealed the detailed latitudinal structure of the diurnal tide near the equator. The GSWM has successfully described the general characteristics of the radar results, although some discrepancies are recognized. In 1996 when radar data are available at all the three sites, the monthly mean values of tidal amplitudes at 90 km agreed very well between Jakarta and Pontianak, while significant discrepancy was found for Christmas Island, suggesting the existence of geographical effects such as non-migrating tides.

Corresponding author E-mail: tsuda@kurasc.kyoto-u.ac.jp

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