26 2 MESOSPHERIC GRAVITY WAVES OBSERVED AT FERRAZ STATION (62° S) DURING 2010-2011 José Valentin Bageston 1,* , Paulo Prado Batista 1 , Delano Gobbi 1 , Neusa M. Paes Leme 2 , Cristiano Max Wrasse 3 1 Instituto Nacional de Pesquisas Espaciais, São José dos Campos, SP, Brazil 2 Instituto Nacional de Pesquisas Espaciais, Centro Regional do Nordeste, Natal, RN, Brazil 3 Vale Soluções em Energia, Av. dos Astronautas, 1758, CEP 12227-010, São José dos Campos, SP, Brazil *e-mail: bageston@gmail.com Abstract: e upper atmosphere above the Sub-Antarctic Islands and Drake Passage is abundant in gravity waves from the troposphere up to the mesosphere. Satellite data and ground based instruments have demonstrated this high gravity wave activity in these regions. Since 2010 an all sky airglow imager has observed gravity waves through the OH NIR airglow emission (~87 km height) over Comandante Ferraz Antarctic Station (62° S) on King George Island. A new-generation meteor radar was installed on that site in 2010 and has been operated simultaneously with an OH airglow imager. e data set of airglow images from 2010 and 2011 is under analyses, and the results from 2010 showed similar characteristics for the waves reported in a campaign carried out in 2007. is work will present the observational results for the gravity waves observed in 2010 and 2011 above King George Island. ese results are composed by the observational statistics for 2010 and 2011, and the observed wave parameters and the preferable propagation directions for the events observed during 2010. Keywords: airglow, atmospheric gravity waves, wave characteristics Introduction The dynamics of the polar mesosphere and lower thermosphere (MLT) are dominated by waves with periods ranging from a few minutes to months (Hibbins et al., 2007). Gravity waves are now recognized to play an important role in the general circulation of the middle atmosphere. Forcing by gravity waves causes reversals of the zonal mean jets and drives a mean meridional transport circulation that leads to a latitudinal temperature gradient opposite to that which would be expected in the absence of wave forcing (Fritts & Alexander, 2003). Espy et al. (2004) reported seasonal variations in the gravity wave momentum flux over Halley Station, Antarctica (75.6° S and 26.6° W). ey used data from a sodium airglow imager and an Imaging Doppler Interferometer (IDI) radar for wind measurements. e authors showed a significant day-to-day variability in the momentum flux, with a strong westward momentum flux that turned eastward around the equinox. Nielsen et al. (2006) used an all-sky imager at Halley Station to show the first bore event observed at high latitudes. Bageston et al. (2009) presented the first airglow observations at Ferraz Station (62.1° S and 58.4° W) based on a full winter data set. ey showed the wave parameters distribution and preferable propagation directions for the waves identified during the austral winter of 2007. Climatology of gravity waves above Halley Station was reported by Nielsen et al. (2009), using airglow data of two consecutive austral winters (2000 and 2001) and including local hourly winds and intrinsic wave parameters. is paper present results for two consecutive austral winters above Ferraz Station (62.1° S, 58.4° W), including example of wave events, statistics of the observations and the observed wave characteristics. http://dx.doi.org/10.4322/apa.2014.056