Contrasting structures between the decoupled and coupled states of the stable boundary layer

• DOI: 10.1002/qj.2693
• Publication Date: 2015-10-23T09:16:39Z
• Authors: Otávio C. Acevedo; Larry Mahrt; Franciano S. Puhales; Felipe D. Costa; Luiz E. Medeiros; Gervásio A. Degrazia
• Keywords: Temperature Gradient

Different aspects of the stable boundary‐layer structure are contrasted between very and weakly regimes from a new point view. This study finds limit wind speed, referred to as crossover threshold , when average vertical gradient turbulent kinetic energy switches sign at all observational levels. When speed exceeds this transition, entire boundary layer becomes vertically fully coupled. Consequently in is considered decoupled regime, while state coupled regime . It shown that profiles other quantities, such friction velocity, heat flux thermal gradients strikingly different two coupling states. Decomposition into temporal scales indicates overlapping non‐turbulent sub‐mesoscale flow with turbulence case, there clearer scale distinction types motions takes place. The budget dominated by dissipation shear production both However, relative importance buoyant destruction term be appreciably larger regime. In equation, magnitude than but not full coupling. These results indicate surface plays major role controlling state, previously proposed. For dataset, frequency distributions quantities near bimodal. modes associated states, each well described independent log‐normal distributions.