Abstract
Abstract. A mesospheric front was observed with an all-sky airglow imager on the night of 9–10 July 2007 at Ferraz Station (62° S, 58° W), located on King George island on the Antarctic Peninsula. The observed wave propagated from southwest to northeast with a well defined wave front and a series of crests behind the main front. The wave parameters were obtained via a 2-D Fourier transform of the imager data providing a horizontal wavelength of 33 km, an observed period of 6 min, and a horizontal phase speed of 92 m s−1. Simultaneous mesospheric winds were measured with a medium frequency (MF) radar at Rothera Station (68° S, 68° W) and temperature profiles were obtained from the SABER instrument on the TIMED satellite. These wind and temperature profiles were used to estimate the propagation environment of the wave event. A wavelet technique was applied to the wind in the plane of wave propagation at the OH emission height spanning three days centered on the front event to define the dominant periodicities. Results revealed a dominance of near-inertial periods, and semi-diurnal and terdiurnal tides suggesting that the ducting structure enabling mesospheric front propagation occurred on large spatial scales. The observed tidal motions were used to reconstruct the winds employing a least-squares method, which were then compared to the observed ducting environment. Results suggest an important contribution of large-scale winds to the ducting structure, but with buoyancy frequency variations in the vertical also expected to be important. These results allow us to conclude that the wave front event was supported by a duct including contributions from both winds and temperature.
Highlights
According to the definitions currently accepted by the scientific community, mesospheric front is a type of gravity wave which presents a frontal airglow emission enhancement or depletion that can be followed by a series of wave crests phase-locked to the leading front (Brown et al, 2004; Smith et al, 2005)
We described a wave front event, followed by a set of ducted waves, observed by an all-sky airglow imager over Ferraz Station on the night of 9–10 July 2007
The ducting environment was assumed to be of large spatial extent, given the extent of the front itself across the full field-of-view of the imager
Summary
According to the definitions currently accepted by the scientific community, mesospheric front is a type of gravity wave which presents a frontal airglow emission enhancement or depletion that can be followed by a series of wave crests phase-locked to the leading front (Brown et al, 2004; Smith et al, 2005). Stockwell et al (2006) applied a S-Transform analysis to the same event reported by Nielsen et al (2006) in order to investigate the dynamical properties of the bore They were able to infer the bore parameters (horizontal wavelength, observed horizontal phase speed, and period) and described its evolution as it propagated. Stockwell et al (2011) analized the vertical wavenumber squared (m2) associated to the bore event reported by Nielsen et al (2006), using the observed wave parameters, hourly wind measurements and MSIS model temperature As they used the S-Transform to acess the bore parameters at distinct times, in the beginning of the observations they identified a free propagating region below 78 km and a evanescent region above this height. Our analysis of the wave characteristics and ducting conditions are discussed in detail below
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
