Calculating the azimuth of mountain waves, using the effect of tilted fine-scale stable layers on VHF radar echoes

摘要

A simple method is described, based onstandard VHF wind-profiler data, where imbalances of echo power between fouroff-vertical radar beams, caused by mountain waves, can be used to calculate theorientation of the wave pattern. It is shown that the mountain wave azimuth(direction of the horizontal component of the wavevector), is given by thevector , ]; ,, , are radar echo powers, measured in dB, in beams pointed away from vertical bythe same angle towards north, south, east and west respectively, and is the vertical wind velocity. The method is applied to Aberystwyth MST radardata, and the calculated wave vector usually, but not always, points into thelow-level wind direction. The mean vertical wind at Aberystwyth, which may alsobe affected by tilted aspect-sensitive layers, is investigated briefly using theentire radar output 1990-1997. The mean vertical-wind profile is inconsistentwith existing theories, but a new mountain-wave interpretation is proposed.Meteorology and atmospheric dynamics (middleatmosphere dynamics; waves and tides; instruments and techniques).