Publication Date:
2011-11-09
Description:
We present the first three-dimensionally resolved observations of polar mesosphere winter echoes obtained with a 25 beam-experiment covering a volume of about 50 km in diameter (horizontal distance) at altitudes between 65 and 85 km. This allows us to resolve the classical space time ambiguity of single beam observations and reveals that the echoing structure was tilted in the East–West direction but showed no considerable tilt in the North–South direction. The Doppler shifts derived from the 24 off-zenith beam directions are consistent with the mean background wind measured independently by a co-located MF-radar. The time development of the 3-D echo-pattern is consistent with scattering structures that follow the constant phase lines of a medium frequency gravity wave that is propagating against the mean flow. Wave parameters derived from these observations are independently confirmed by the analysis of co-located wind measurements with the aforementioned MF-radar. Overall, the observed echo morphology in time and space is reminiscent of gravity wave breaking which is known to lead to a maximum of turbulence activity that moves with the phase of the wave.
Print ISSN:
0148-0227
Topics:
Geosciences
,
Physics
