Acoustic Sounder Observations of the Dissipation of Nocturnal Surface Inversions over Ridge and Valley Terrain

Abstract Acoustic sounder data show that over the Highveld of South Africa nocturnal inversions do not dissipate beneath an absolutely stable layer with a constant upper surface height. Instead. penetrative convection and entrainment lift and weaken the echo envelope of the surface inversion so that it slopes upwards with time. Final dissipation is shown to take place at heights exceeding the original inversion-top height by a factor of two to three. Ridge and valley dissipation characteristics are compared and fumigation times for Riven heights of pollution emission are presented.

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