THE WIND REGIME OF THE MESOSPHERE AND LOWER THERMOSPHERE DURING THE DYANA CAMPAIGN .1. PREVAILING WINDS

During the DYANA campaign, winds and tides at mesopheric and lower the rmospheric altitudes were measured by 14 ground based experiments (MF radars, meteor radars and LF-drift systems). The experiments were loca ted between 107-degrees-W and 102-degrees-E, mostly in northern mid-la titudes with well covered areas in Central and Eastern Europe. Emphasi s is placed here upon the vertical profiles and height-time contours o f the prevailing zonal and meridional winds with different resolution (15 d, 4 d). Generally, westerly winds are observed at heights below 9 5 km with a strong mesospheric variability and with longitudinal diffe rences between the data of Central Europe, Eastern Europe, Asia and Ca nada. Planetary waves and a minor stratospheric warming in the first 1 0 days of February 1990 are the cause of this behaviour. In connection with the stratospheric warming, a wind reversal to summer east winds reaching from the upper stratosphere up to 95 km is observed. The clos e connection of the behaviour of the stratosphere with the observed lo ngitudinal differences in the mesospheric response on the stratospheri c warming and with the occurrence of wind oscillations (10-15 d) is di scussed.