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A case study of mesospheric planetary waves observed over a three-radar network using empirical mode decomposition

Abstract. In this paper an attempt is made to study equatorial Kelvin waves using a
network of three radars: Kototabang
(0.204∘ S, 100.320∘ E)
meteor radar, Pameungpeuk (7.646∘ S, 107.688∘ E)
medium-frequency radar, and Pontianak
(0.003∘ S, 109.367∘ E) medium-frequency radar. We have used
the continuous data gathered from the three radars during April–May 2010.
Empirical mode decomposition (EMD), Lomb–Scargle periodogram (LSP) analysis,
and wavelet techniques are used to study the temporal and altitude structures
of planetary waves. Here, we used a novel technique called EMD to extract the
planetary waves from wind data. The planetary waves of ∼ 6.5 and
∼ 3.6 days periodicity are observed in all three radar stations with
peak amplitudes of about 12 and 11 m s−1, respectively. The 3.6-day
wave has an average vertical wavelength from the three radars of about
42 km. The 3.6- and 6.5-day planetary waves are particularly strong in the
zonal wind component. We find that the two waves are present at the
84–94 km height region. The observed features of the 3.6- and 6.5-day waves
at the three tropical-latitude stations show some correspondence with the
results reported for the equatorial-latitude stations. Keywords. Electromagnetics (wave propagation) – history of geophysics (atmospheric sciences) – meteorology and atmospheric dynamics (middle atmosphere dynamics) 
