GRAVITY-WAVE ACTIVITY AND ITS RELATION WITH PREVAILING WINDS DURING DYANA

The DYANA campaign in early 1990 gave a unique opportunity to study the gravity wave (GW) activity in the middle atmosphere in relation to the general circulation. Several instruments, including Rayleigh lidar, MF and meteor radars, OH and O2 spectrometers and radio-wave absorption receivers provided data at various locations in Europe and Canada to study the GW activity during the campaign. These sets of data indicate that the GW activity is in general enhanced during periods of strong westerly prevailing winds or high planetary-wave activity in the middle atmosphere. When two sets of data are compared, they show a rather fast decorrelation as a function of altitude difference or horizontal distance. This study confirms that the level of GW activity in the middle atmosphere is very sensitive to filtering by the mean wind, but does not exclude its sensitivity to the sources of GW.