Investigating the potential triggering mechanisms of turbulence intermittency in the Arctic Boundary Layer

The turbulence in the Arctic is often observed to be intermittent as a result of the interaction with non-turbulent motions. Several studies have examined the triggering mechanisms behind the intermittency, yet the understanding of their influence is still insufficient. In this study, turbulence intermittency in the Arctic stable boundary layer is investigated using observations from the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition, spanning October 2019 to September 2020. Turbulent and sub-mesoscale motions separated using Multi-Resolution Decomposition (MRD) cospectral analysis are used to quantify the strength of turbulent and sub-meso motions. Previous study showed the evolution of intermittency under strong stratification, when sub-mesoscale energy exceeds 10% of the total mean kinetic energy. While such clear indications are not evident in this available data, we further examine the role of additional factors such as radiative forcing or cloud cover, in the triggering of intermittency in turbulence in this region. The triggering mechanisms are analyzed separately for polar night and polar day regimes, using different radiative forcing thresholds. The study is further extended to analyze the stability correction function (φ) and assess the validity of the classic Monin-Obhukov Similarity Theory (MOST) under such motions. These results are compared with the generalized stochastic model to assess its ability to represent these non-stationary motions associated with intermittency. Following the outcome, the stochastic model may be refined to better capture intermittent turbulence processes in the Arctic.