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The atmosphere background wind field controls the propagation ofgravity waves from the troposphere through the stratosphere into themesosphere. During January 2003 the MaCWAVE campaign took place atEsrange, with the purpose of observing vertically ascending wavesinduced by orography. Temperature data from the U. Bonn lidar atEsrange (68° N/21° E) and the ALOMAR RMR lidar(69° N/16° E), wind data from Esrange MST radarESRAD, as well as wind data from the ECMWF T106 model, are used toanalyse the atmospheric background situation and its effect onmountain wave propagation during January/February 2003. Criticallevels lead to dissipation of vertically ascending waves, thusmountain waves are not observable above those levels. In the firsthalf of January a minor as well as a major stratospheric warmingdominated the meteorological background situation.  These warmingsled to a wind reversal, thus to critical level filtering andconsequently prevented gravity waves from propagating to highaltitudes. While the troposphere was not transparent for stationarygravity waves most of the time, there was a period of eight daysfollowing the major warming with a transparent stratosphere, withconditions allowing gravity waves generated in the lower troposphereto penetrate the stratosphere up to the stratopause and sometimeseven into the lower mesosphere. In the middle of February a minorstratospheric warming occurred, which again led to critical levelssuch that gravity waves were not able to ascend above the middlestratosphere. Due to the unfavourable troposphere and lowerstratosphere conditions for gravity wave excitation and propagation,the source of the observed waves in the middle atmosphere isprobably different from orography

The atmospheric background situation in northern Scandinavia during January/February 2003 in the context of the MaCWAVE campaign