Abstract
Abstract. The atmosphere background wind field controls the propagation of gravity waves from the troposphere through the stratosphere into the mesosphere. During January 2003 the MaCWAVE campaign took place at Esrange, with the purpose of observing vertically ascending waves induced by orography. Temperature data from the U. Bonn lidar at Esrange (68° N/21° E) and the ALOMAR RMR lidar (69° N/16° E), wind data from Esrange MST radar ESRAD, as well as wind data from the ECMWF T106 model, are used to analyse the atmospheric background situation and its effect on mountain wave propagation during January/February 2003. Critical levels lead to dissipation of vertically ascending waves, thus mountain waves are not observable above those levels. In the first half of January a minor as well as a major stratospheric warming dominated the meteorological background situation. These warmings led to a wind reversal, thus to critical level filtering and consequently prevented gravity waves from propagating to high altitudes. While the troposphere was not transparent for stationary gravity waves most of the time, there was a period of eight days following the major warming with a transparent stratosphere, with conditions allowing gravity waves generated in the lower troposphere to penetrate the stratosphere up to the stratopause and sometimes even into the lower mesosphere. In the middle of February a minor stratospheric warming occurred, which again led to critical levels such that gravity waves were not able to ascend above the middle stratosphere. Due to the unfavourable troposphere and lower stratosphere conditions for gravity wave excitation and propagation, the source of the observed waves in the middle atmosphere is probably different from orography.
Highlights
The Scandinavian mountain ridge is a major source for the excitation of gravity waves in the Arctic polar atmosphere (e.g. Volkert and Intes, 1992; Schoch et al, 2004)
The Arctic winter atmosphere during January and February 2003 was dominated by one minor and one major stratospheric warming in the first half of January, which led to a wind reversal in the middle stratosphere and to critical level filtering of vertically ascending gravity waves
Due to a critical level filtering at about the 45–60 km altitude, stationary mountain waves were not able to penetrate into the mesosphere
Summary
The Scandinavian mountain ridge is a major source for the excitation of gravity waves in the Arctic polar atmosphere (e.g. Volkert and Intes, 1992; Schoch et al, 2004). Bonn lidar at Esrange (68◦ N/21◦ E), located near the city of Kiruna in northern Sweden (Blum and Fricke, 2005), and the ALOMAR RMR lidar (69◦ N/16◦ E) located on the Norwegian island of Andøya (von Zahn et al, 2000), were operated during January and February 2003 on both sides of the Scandinavian mountains. Able to derive temperature profiles from the middle stratosphere to the mesosphere, assuming hydrostatic equilibrium and integrating the range corrected lidar net signal (Kent and Wright, 1970; Hauchecorne and Chanin, 1980) These measurements cover almost continuously the time period from 2 January to 19 February 2003 and give an exhaustive overview of the atmospheric temperature development above northern Scandinavia near the Arctic circle. As PSC form regularly in temperature minima caused by atmospheric gravity waves (e.g. Carslaw et al, 1998; Dornbrack and Leutbecher, 2001; Blum et al, 2005, and references therein), the atmospheric dynamics are of interest for this research
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