Influência em curta duração de ondas planetárias na dinâmica das marés atmosféricas observadas nos ventos meteóricos de São João do Cariri-PB.

Abstract

The Atmospheric Tides are among the most prominent motions in the Mesosphere and Lower Thermosphere (MLT), often dominating the wind field at low latitudes. The variations in atmospheric circulation verified in the MLT region are, in large part, due to the propagation of waves which, in general, are caused by dynamic processes in the lower layers of the atmosphere and propagate horizontally and vertically upward, reaching the highest levels. In this region, tides present intense amplitude and its effect must be considered to explain the dynamics characteristics of the near mesopausa region. The characteristics of the Atmospheric Tides in the horizontal winds between 80 and 100 km, observed at São João do Cariri-PB, had been studied recently. In accordance with results of this study, the amplitude of the Atmospheric Tides shows variability throughout the time. Through studies based on numerical models and observations, it was pointed out that the tidal amplitudes exhibit variability extending from the scale of days to years. In this Thesis, Wavelets Analysis, Harmonic Analysis, Power Spectral Density and Bispectral Analysis were applied to hourly data obtained from meteor winds, between the years 2004 and 2008, using meteor radars installed in São João do Cariri-PB (7,4°S, 36,5°W) and Cachoeira Paulista-SP (22,7°S, 45,0°W), to investigate the variability, in periods of Planetary Waves, of the Atmospheric Tide amplitudes in these region. Spectral components present in the meteor winds in the MLT region, which do not have explanations through known mechanisms, are associated with resonant nonlinear interactions between Atmospheric Tides and Planetary Waves. These interactions result in the amplitude modulation of the tide by Planetary Waves and, consequently, the production of secondary spectral components by sum and/or difference of primary oscillations frequencies. Therefore, the accomplished investigations, in this Thesis, were focused in the resonant nonlinear interaction as an important mechanism to explain the variability of the tidal in periods of Planetary Waves. Additionally, it was studied the influence of one event of Sudden Stratospheric Warming in the amplitudes of the tides and Quasi-Two Day Wave (QTDW) in the MLT of São João do Cariri-PB. We concluded the research making the comparison of some results obtained in Cachoeira Paulista - SP with those of São João of Cariri - PB.