Abstract
Abstract. On 16–17 July 2007 during an observational campaign at Comandante Ferraz Antarctic Station (62° S, 58° W), a mesospheric wall was observed with an airglow all-sky imager. The wave appeared like an extensive dark region in the all-sky airglow images, with a large depletion in the OH emission. Simultaneous mesospheric winds measured with a MF radar at Rothera station and temperature profiles from SABER instrument, on board of TIMED satellite, were used to obtain the propagation condition of the wave. Wind measurements during four days, around the time of observation of the wave, are presented in order to discuss the type and consistence of the duct in which this wave was propagating. By using wavelet analysis and tidal amplitude components we found that 12 and 8 h components were the most important periodicities around the time interval of the wave observation. A collocated imaging spectrometer, for mesospheric temperature measurements, has been operated simultaneously with the all-sky imager. Direct effects of the mesospheric front have been seen in the spectrometric measurements, showing an abrupt decrease in both OH intensity and rotational temperature when the wave front passes overhead. The main contribution of the present work is the investigation of the type of duct in which the wall event was propagating. We found evidences for a thermal duct structure to support the mesospheric wall propagation. This result was obtained by two types of analysis: (a) the tidal components analysis and winds filtering (harmonic analysis), and (b) comparison between the terms of the m2 dispersion relation.
Highlights
The mesospheric fronts and specially bore events (Dewan and Picard, 1998), have been extensively reported at low and mid latitudes (Taylor et al, 1995; Smith et al, 2003; Medeiros et al, 2005; Fechine et al, 2005)
2 Observation and data analysis During an observational campaign (Bageston et al, 2009) focused on characterizing the gravity waves observed at Comandante Ferraz Antarctic Station (62.1◦ S, 58.4◦ W), we have identified three uncommon gravity waves events – the so called mesospheric fronts
The main results presented in this work are the following: (a) we report first measurements of mesospheric wall over Antarctica; (b) analysis show the observed mesospheric front was supported by thermal duct; (c) the effects of this front was noted in OH rotational temperature and band intensity
Summary
The mesospheric fronts and specially bore events (Dewan and Picard, 1998), have been extensively reported at low and mid latitudes (Taylor et al, 1995; Smith et al, 2003; Medeiros et al, 2005; Fechine et al, 2005). Based on Na lidar, meteor radar and all-sky airglow images, Batista et al (2002) reported simultaneous observation of sporadic sodium layer, mesospheric winds and wall event at Cachoeira Paulista (23◦ S). Nielsen et al (2006) using an all-sky imager at Halley station, Antarctica (75.5◦ S), reported the first bore event observed at high latitudes This wave event was seen in three different airglow layers (OH, Na, and O2) and persisted on the image for a long time (∼3 h). The characteristics of the bore event were determined by applying the S-Transform analysis (Stockwell et al, 2006) The occurrence of these sorts of events would be associated with a temperature inversion layer that acts as a wave duct. For more details of the campaign and the first results see Bageston et al (2009)
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