A SELF-ORGANIZED CRITICALITY ANALOGY OF SUBMESO MOTIONS AND INTERMITTENT TURBULENCE ACROSS A NOCTURNAL LOW-LEVEL JET.

The switching between turbulent (active) and non-turbulent (passive) states is one of the distinctive features of stable boundary layer (SBL). In very stable conditions, the SBL becomes layered with fully developed turbulence confined to a narrow region near the surface and weak and intermittent turbulence detached from the ground in the quiescent region above, frequently associated to the development of a low-level jet (LLJ). The classical Monin-Obukhov similarity theory fails in the layered SBL because of the switching between active and passive states, and quantifying mixing and transport properties becomes challenging in numerical models. In this work, multi-level high frequency time series from a tall (140 m) meteorological tower are analysed by Telegraphic Approximation to identify connections between SBL states and a general class of intermittency models that include self-organised criticality (SOC). The analysed night includes transition from a mildly SBL to one dominated by LLJ and quiescent layers with weak or intermittent turbulence. Aspects of the submeso motions that setup after the formation of the LLJ are shown to carry signatures of co-existence of self-organized criticality (SOC) and intermittent turbulence. The observed behaviour in clustering and intermittency exponents indicates that the submeso motions are highly clustered and their influence enhanced intermittent turbulence both in the inertial subrange and at larger scales. The switching probability of active-inactive states and lifetimes of inactive states (related to intermittent turbulent burst) shows evidence of SOC-like behaviour in terms of scaling laws. The coexistence of SOC and intermittent turbulence in the SBL may offer new perspective about the genesis of scaling laws and similarity arguments improving performances of meteorological and dispersion models in stable atmosphere.