Abstract
Abstract. This study investigates the characteristics of the quasi 16-day wave in the mesosphere during boreal winter 2011/2012 using observations of water vapor from ground-based microwave radiometers and satellite data. The ground-based microwave radiometers are located in Seoul (South Korea, 37° N), Bern (Switzerland, 47° N) and Sodankylä (Finland, 67° N). The quasi 16-day wave is observed in the mesosphere at all three locations, while the dominant period increases with latitude from 15 days at Seoul to 20 days at Sodankylä. The observed evolution of the quasi 16-day wave confirms that the wave activity is strongly decreased during a sudden stratospheric warming that occurred in mid-January 2012. Using satellite data from the Microwave Limb Sounder on the Aura satellite, we examine the zonal characteristics of the quasi 16-day wave and conclude that the observed waves above the midlatitudinal stations Seoul and Bern are eastward-propagating s = −1 planetary waves with periods of 15 to 16 days, while the observed oscillation above the polar station Sodankylä is a standing wave with a period of approximately 20 days. The strongest relative wave amplitudes in water vapor during the investigated time period are approximately 15%. The wave activity varies strongly along a latitude circle. The activity of the quasi 16-day wave in mesospheric water vapor during boreal winter 2011/2012 is strongest over northern Europe, the North Atlantic Ocean and northwestern Canada. The region of highest wave activity seems to be related to the position of the polar vortex. We conclude that the classic approach to characterize planetary waves zonally averaged along a latitude circle is not sufficient to explain the local observations because of the strong longitudinal dependence of the wave activity.
Highlights
The dynamical regime of the extratropical middle atmosphere is characterized by waves and tides, in particular by global-scale planetary waves during wintertime
The relative amplitudes were calculated by dividing the absolute amplitudes by the average water vapor volume mixing ratio (VMR) within the considered time period at each pressure level
We have shown observations of the quasi 16-day wave in mesospheric water vapor during boreal winter 2011/2012 obtained by ground-based microwave radiometers and complemented by satellite data
Summary
The dynamical regime of the extratropical middle atmosphere is characterized by waves and tides, in particular by global-scale planetary waves during wintertime. The vertical propagation of planetary waves leads to wave breaking at higher altitudes due to the decrease in air density, which in turn results in wave–meanflow interaction, which is known to be a major driver of atmospheric dynamics in the wintertime middle atmosphere (Andrews et al, 1987). Such wave–mean-flow interaction can drastically alter the zonal mean flow, e.g., during a sudden stratospheric warming (SSW), and is believed to be the main mechanism for the onset of a SSW (Matsuno, 1971). Observations have shown that the time period before the onset of a SSW is often characterized by high wave activity (e.g., Hirota et al, 1990; Sivjee et al, 1994; Jacobi et al, 2003)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
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 call
