Local Structure of Turbulence in Stably Stratified Boundary Layers

Abstract

The ?flux based? local scaling in the stably stratified boundary layer is valid only in cases with strong, continuous turbulence, when the gradient Richardson number Ri is constant and subcritical. To extend the local similarity approach to cases with weak turbulence (very stable regime), the ?gradient based? local scaling is introduced and discussed in the paper. Both types of local scaling, the flux based and the gradient based, are tested based on the data, collected from a 60-m tower during the Cooperative Atmosphere?Surface Exchange Study-1999 (CASES-99). The obtained results show that the gradient-based scaling provides a useful framework for the treatment of cases with both strong and weak turbulence and overcritical Richardson numbers.