Extended Abstract (84K)13.4
Dynamic airflow channelling effects in bent valleys
Meinolf Kossmann, University of Canterbury, Christchurch, New Zealand; and A. P. Sturman
Previous investigations of dynamic channelling of airflow in mountain valleys have been limited to straight valleys, where a constant along-valley component of the synoptic pressure gradient can be assumed. In nature, however, valleys are often curved or bent, i.e. composed of (multiple) segments of different orientation. In these valleys, the along-valley component of the synoptic-scale pressure gradient differs from one segment of the valley to another. This paper presents a simple conceptual model of the changes in wind speed and direction that will occur along the axis of a bent valley due to pressure driven channelling when adjacent linear valley segments have different orientation, but constant width and depth. Special emphasis is given to horizontal flow convergence or divergence and compensatory lifting or subsidence within (and above) the valley. The processes are discussed for situations where differently orientated but straight adjacent valley segments form a bent valley, but the results can easily be adapted to smoothly curving valleys. The expected effects of the magnitude of the angle between segments (or, alternately, valley curvature) on the expected flow patterns in the valley are analysed. The conceptual model derived for flow patterns in curved or bent valleys has a wide range of applications in mountainous terrain including the dispersion of air pollutants, convective cloud development, wind energy potential and aviation.
Session 13, Gap Winds and Foehn I
Thursday, 20 June 2002, 8:00 AM-10:30 AM
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