Research progress and current application of weak turbulence and turbulence intermittency in stable boundary layers

Abstract

Research on the stable boundary layer is not only a scientific challenge but is also the foundation of studies on the atmospheric environment, weather, and climate change, with significant practical value in social and economic development. Starting from the mutual transitions between weakly and strongly stable boundary layer states, we review the research progress and application of weak turbulent motions and turbulence intermittency. Turbulent intermittency can be driven by internal (the feedback interaction of wind shear and stability) and external factors (sub-mesoscale motions). We clarified the interaction mechanism between the internal and external factors of turbulent intermittency and elucidated how the interaction affects the evolution of stable boundary layer. Given the widespread existence and importance of sub-mesoscale motion, by separating and quantitatively characterizing sub-mesoscale and turbulent motions from the complex flow fields of stable boundary layers, turbulence intermittency can be identified and quantitatively characterized. Accordingly, the typical characteristics of alternating quiescent and bursting periods of turbulence intermittency events can be determined. Notably, during weak turbulence and quiescent periods of turbulence intermittency, the turbulent transport of matter and energy can be affected by sub-mesoscale motions, has been overestimated easily, relevant corrections are necessary. Eliminating the effects of sub-mesoscale motions can improve the similarity relationships of the stable boundary layers. Moreover, non-stationary turbulent transport during bursting periods of turbulence intermittency events will change the general understanding of classical problems. For example, the surface energy closure rate during the bursting periods can even be very close to totally closure. Turbulence intermittency has wide applications. In this study, turbulence intermittency is combined with haze pollution research to propose the concept of the turbulence barrier effect and investigate the physical mechanisms through which turbulence barriers can be strengthened or broken. The turbulence barrier effect significantly affects turbulent transport of matter, such as carbon dioxide and water vapor; thus, it is vital in practical issues, such as early warning for dust storms and dense fog events. However, three key challenges still require further investigation: physical mechanisms of state transitions and mechanisms of vertical structure evolution in stable boundary layers; physical origins, spatial and temporal evolution patterns, and parameterization of turbulence intermittency; and improvement of the similarity theory of stable boundary layers. Finally, we discussed future research directions on weak turbulence and turbulence intermittency in stable boundary layers, and explored the potential applications of observational facts, theoretical breakthroughs, and simulation advances in stable boundary layers to improve air pollution forecasts, extreme weather warning, and climate change projections.