Abstract
Abstract. The quasi 2 day wave (QTDW) over Collm (51° N, 13° E) has been studied between September 2004 and September 2013 using a VHF meteor radar. The 9 year mean amplitudes show a strong summer maximum with several irregular bursts and much weaker winter maxima. In summer, the meridional amplitude is slightly larger than the zonal one with about 15 m s−1 at 91 km height. Phase differences are slightly higher than 90°, which indicates a polarization that is nearly circular. On an average the QTDW is amplified after a maximum of zonal wind shear. This can be realized in the summer mesospheric jet where the zonal wind component has its minimum or, in other words, the easterly jet maximizes. Thus, instability is found as a likely forcing mechanism. QTDW amplitudes exhibit considerable inter-annual variability. In particular, there is a possible relation between the QTDW amplitude and the 11-year solar cycle in winter but not in summer.
Highlights
The quasi 2 day wave (QTDW) is one of the most striking dynamical features in the mesosphere and lower thermosphere
In the following we report some features of the summer QTDW as seen by the radar
We find maximum QTDW amplitudes on an average 10 days after maximum wind shear
Summary
The quasi 2 day wave (QTDW) is one of the most striking dynamical features in the mesosphere and lower thermosphere. A local climatology of QTDW amplitudes and phases over Collm as seen by ground-based radio measurements in the low-frequency (LF) range is already available (Jacobi et al, 1997). Their results base on measurements with regular daily data gaps, which may affect wave analysis and lead to uncertainties of amplitude and phase detection. The earlier LF spaced receiver method that has been applied at Collm since the late 1950s until 2007 was based on the reflection of commercial LF radio waves in the lower ionospheric E region This led to regular daily gaps due to increased absorption during daylight hours, long in summer. This is in agreement with the results of Jacobi et al (1997) who showed that the resulting error of the amplitudes and phases for a period of 48 h with respect to the true values is small
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