ANGEO Annales Geophysicae ANGEO Ann. Geophys. 1432-0576 Copernicus Publications Göttingen, Germany 10.5194/angeo-27-1059-2009 Seasonal variations in gravity wave activity at three locations in Brazil Clemesha B. R. 1 Batista P. P. 1 Buriti da Costa R. A. 2 Schuch N. 3 Instituto Nacional de Pesquisas Espaciais, São José dos Campos, SP, Brazil Universidade Federal de Campina Grande, Campina Grande, PB, Brazil Centro Regional Sul de Pesquisas Espaciais – INPE, Santa Maria, RS, Brazil 04 03 2009 27 3 1059 1065 Copyright: © 2009 B. R. Clemesha et al. 2009 This work is licensed under the Creative Commons Attribution 3.0 Unported License. To view a copy of this licence, visit https://creativecommons.org/licenses/by/3.0/ This article is available from https://angeo.copernicus.org/articles/27/1059/2009/angeo-27-1059-2009.html The full text article is available as a PDF file from https://angeo.copernicus.org/articles/27/1059/2009/angeo-27-1059-2009.pdf

Using the variance in meteor radar winds as a measure of gravity wave activity, we investigate the temporal variations in gravity waves at three locations in Brazil: São João do Cariri (7.3° S, 36.4° W), Cachoeira Paulista (22.7° S, 45.0° W) and Santa Maria (29.7° S, 53.7° W). The technique used is that of Hocking (2005) which makes it possible to separate the zonal and meridional components of the fluctuating wind velocity. We find that the seasonal variation of the fluctuating wind is similar to that of the amplitude of the diurnal tide, showing a predominantly semi-annual variation, stronger at Cachoeira Paulista and Santa Maria than at the quasi-equatorial station, Cariri. Both with respect to the seasonal trend and shorter term variations, strong coupling between gravity wave activity and tides is indicated by a remarkably close correlation between the fluctuating velocity and the vertical shear in the tidal winds. It is not clear as to whether this is caused by gravity wave forcing of the tides or whether it results from in situ generation of gravity waves by tidal wind shear.

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