Radio Science

Tilted atmospheric layer and gravity wave studies by simultaneous DBS/SDI observations with the MU radar during the passage of a trough

Authors

  • Noriyuki Kawano,

  • Hubert Luce,

  • Mamoru Yamamoto,

  • Shoichiro Fukao


Abstract

In the present paper, simultaneous radar observations in Doppler beam swinging (DBS) and spatial domain interferometry (SDI) modes with the middle and upper atmosphere (MU) radar are shown for the first time. High aspect sensitive echo layers were found at a 6.0 to 8.6 km altitude range owing to observations in DBS mode. From SDI analysis, the angle of arrival of the backscattered signals was also deduced. It was found that the layers were tilted from the horizontal plane along the zonal axis with a tilt angle of approximately 0.7°. Because it is known that tilted aspect sensitive layers introduce a bias in the radial velocity measurements, we corrected the vertical velocities directly measured by the vertical beam in DBS mode, by taking account of the tilt angle of the layers estimated by the SDI technique. On the other hand, from the analysis of horizontal wind profiles, we observed a quasi-monochromatic gravity wave related to the tilted layers. It was found that the tilt angle of the phase of wave front is well associated with the inclination of the echo layers if the corrected vertical velocity is used. Finally, the Richardson number estimated at an altitude range where the aspect sensitive echo layers occur presents large positive peaks at the position of the aspect sensitive echo layers and then seems to be too high for turbulent instabilities. Consequently, the observed echo layers may be stable layers at the most stable phase of the gravity wave.

Ancillary