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Session: Atmospheric turbulence 1
Session starts: Tuesday 25 August, 10:30
Presentation starts: 10:45
Room: Room C

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Ivo van Hooijdonk (Eindhoven University of Technology)
Judith Donda (Eindhoven University of Technology)
Fred Bosveld (KNMI)
Arnold Moene (Wageningen University)
Herman Clercx (Eindhoven University of Technology)
Bas van de Wiel (Eindhoven University of Technology)

Abstract:
In some nights, the near-surface temperature can drop dramatically and turbulence in the stably stratified boundary layer becomes very weak, such that the lfow reaches a (quasi-) laminar state. In other cases, however, the atmosphere remains in a turbulent state and temperatures stay relatively high. Recently, the appearance of two distinct boundary layer regimes was explained by a new theoretical framework. This theory builds on the fact that the turbulent heat flux in stably stratified flow is limited to a maximum for given wind shear. This introduces a characteristic flux-based velocity scale, which can be used to predict the regimes. This hypothesis is consistent with field observations and numerical results. Also, the hypothesis is generalised to a dimensionless framework.