Statistical investigations of flow structures in different regimes of the stable boundary layer

TL;DR

This paper uses non-stationary time series analysis to investigate flow structures and turbulence regimes in the stable boundary layer, revealing different scale interactions and flow events associated with various stability conditions.

Contribution

It introduces a novel combination of methods to analyze non-stationary turbulence data, identifying distinct flow regimes and their associated structures in the stable boundary layer.

Findings

Different turbulence regimes exhibit distinct scale separation.

Flow structures related to submeso motions are identified.

Stable stratification influences turbulence and flow event scales.

Abstract

A combination of methods originating from non-stationary timeseries analysis is applied to two datasets of near surface turbulence in order to gain insights on the non-stationary enhancement mechanism of intermittent turbulence in the stable atmospheric boundary layer (SBL). We identify regimes of SBL turbulence for which the range of timescales of turbulence and submeso motions, and hence their scale separation (or lack of separation) differs. Ubiquitous flow structures, or events, are extracted from the turbulence data in each flow regime. We relate flow regimes characterised by very stable stratification but different scales activity to a signature of flow structures thought to be submeso motions.