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Falling sphere and balloon wind and temperature data from the MaCWAVE wintercampaign, which was conducted in northern Scandinavia during January 2003,are analyzed to investigate gravity wave characteristics in the stratosphereand mesosphere. There were two stratospheric warming events occurring duringthe campaign, one having a maximum temperature perturbation at ~45 kmduring 17–19 January, and the other having a maximum perturbation at ~30 kmduring 24–27 January. The former was a major event, whereas the latterwas a minor one. Both warmings were accompanied by upper mesosphericcoolings, and during the second warming, the upper mesospheric coolingpropagated downward. Falling sphere data from the two salvos on 24–25 Januaryand 28 January were analyzed for gravity wave characteristics. Gravity waveperturbations maximized at ~45–50 km, with a secondary maximum at~60 km during Salvo 1; for Salvo 2, wave activity was most pronouncedat ~60 km and above.<P  style="line-height: 20px;">Gravity wave horizontal propagation directions are estimated using theconventional hodographic analysis combined with the S-transform (a Gaussianwavelet analysis method). The results are compared with those from a Stokesanalysis. They agree in general, though the former appears to provide betterestimates for some cases, likely due to the capability of the S-transform toobtain robust estimates of wave amplitudes and phase differences betweendifferent fields.<P  style="line-height: 20px;">For Salvo 1 at ~60 km and above, gravity waves propagated towards thesoutheast, whereas for Salvo 2 at similar altitudes, waves propagatedpredominantly towards the northwest or west. These waves were found not to betopographic waves. Gravity wave motions at ~45–50 km in Salvo 1 weremore complicated, but they generally had large amplitudes, short verticalscales, and their hodographs revealed a northwest-southeast orientation. Inaddition, the ratios between wave amplitudes and intrinsic phase speedsgenerally displayed a marked peak at ~45–50 km and decreased sharply at~50 km, where the background winds were very weak. These resultssuggest that these wave motions were most likely topographic wavesapproaching their critical levels. Waves were more nearly isotropic in thelower stratosphere

Gravity waves in the middle atmosphere during the MaCWAVE winter campaign: evidence of mountain wave critical level encounters