Abstract
Abstract. The winter MaCWAVE (Mountain and convective waves ascending vertically) rocket campaign took place in January 2003 at Esrange, Sweden and the ALOMAR observatory in Andenes, Norway. The campaign combined balloon, lidar, radar, and rocket measurements to produce full temperature and wind profiles from the ground to 105 km. This paper will investigate gravity wave propagation in the mesosphere and lower thermosphere using data from the Weber sodium lidar on 28–29 January 2003. A very large semidiurnal tide was present in the zonal wind above 80 km that grew to a 90 m/s amplitude at 100 km. The superposition of smaller-scale gravity waves and the tide caused small regions of possible convective or shear instabilities to form along the downward progressing phase fronts of the tide. The gravity waves had periods ranging from the Nyquist period of 30 min up to 4 h, vertical wavelengths ranging from 7 km to more than 20 km, and the frequency spectra had the expected –5/3 slope. The dominant gravity waves had long vertical wavelengths and experienced rapid downward phase progression. The gravity wave variance grew exponentially with height up from 86 to 94 km, consistent with the measured scale height, suggesting that the waves were not dissipated strongly by the tidal gradients and resulting unstable regions in this altitude range.
Highlights
The MaCWAVE winter campaign in January 2003 involved 2 sounding rockets and 46 MET rockets launched from ESRANGE, Sweden, 51 balloons launched from ESRANGE and Andoya Rocket Range/ALOMAR, Norway, and radar and lidar data collection at both locations
Convective or dynamical in nature. This proves to be a significant simplification, in general, as there are a multitude of instabilities that can arise, and these depend on the specific characteristics of the flow, the amplitudes and intrinsic properties of the involved waves, the initial conditions at the time of instability occurrence, and the influences of viscosity and thermal diffusivity (Achatz, 2005; Fritts et al, 2006; Lombard and Riley, 1996; Sonmor and Klaassen, 1997; see Fritts and Alexander, 2003, for a review of these dynamics)
We have looked at the semidiurnal tide and investigated the conditions for instability on this night
Summary
The MaCWAVE winter campaign in January 2003 involved 2 sounding rockets and 46 MET rockets launched from ESRANGE, Sweden, 51 balloons launched from ESRANGE and Andoya Rocket Range/ALOMAR, Norway, and radar and lidar data collection at both locations. Mountain waves were present during the first winter salvo (24 January 2003) below ∼65 km, but were prevented from penetrating to higher altitudes by a zonal wind reversal due to a stratospheric warming (Wang et al, 2006). A second rocket sequence on 28–29 January 2003 observed a large amplitude semidiurnal variation and superposed high-frequency motions observed with lidar and radar instrumentation at ESRANGE and ARR/ALOMAR. This paper will concentrate on the amplified semidiurnal tide on 28–29 January 2003, the resultant regions of possible instability, and the residual gravity wave (GW) field
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