Resumen

MOTA LIMA, L et al. 3-4 day Kelvin waves observed in the MLT region at 7.4° S, Brazil. Geofís. Intl [online]. 2008, vol.47, n.3, pp.153-160. ISSN 2954-436X.

Meteor wind measurements obtained from São João do Cariri-PB (7.4° S, 36.5° W), Brazil, during 2005, have been used to examine the ultra-fast Kelvin wave characteristics in the mesopause and lower thermosphere region. The hourly winds were subjected to wavelet analysis and the results revealed the presence of 3-4 day oscillation in four episodes along the year. The observed parameters were used to check if the 3-4 days oscillations satisfy the dispersion relation for Kelvin waves. The results showed that only the oscillations that occurred in February-March and May-June (first and second events), are compatible with equatorial ultra-fast Kelvin wave propagation, with zonal wave number s=1. During these two events, the zonal wind amplitudes reached maximum values of 25 m/s and 20 m/s respectively. The vertical phase structure showed descending phase, compatible with ascending wave energy, and vertical wavelengths of about 40 km were found for both events.

Palabras llave : Kelvin Waves; upper atmosphere; aeronomy; atmospheric dynamics; meteor radar.