6 - Who’s afraid of the dark: The not so stable stable boundary layer

Abstract

In this chapter we explore the main features of the stable boundary layer (SBL), which includes the evening transition from convective to stable conditions; the growth of a surface-based temperature inversion; the relative roles of turbulence and long-wave radiational cooling in maintaining the SBL; turbulence regimes; the nocturnal low-level jet; turbulence intermittency; and bursting events. Turbulence in a stably stratified flow is not well understood, but reasonable predictions can be made for weakly stratified flows. As stratification increases, disruptions in the turbulent flow increase and model predictions become more uncertain. Under very strong stratification (e.g., clear skies and calm winds), a traditional SBL may not exist. The non-stationarity of intermittent turbulence impacts the calculations of mean quantities. Within the atmospheric research community, the SBL is an area of intense interest and study. Because of its complexity, within the air quality community, the SBL is an area of great importance because predictions are less reliable.