Understanding turbulent kinetic energy (TKE) stationarity within a forest canopy

Year round measurements of turbulence were taken at heights, above, below, and in the live crown in an old-growth forest in Howland, ME. A technique to determine the stationarity of turbulence kinetic energy (TKE) is presented and used as a classifier of the turbulence intermittency in the nocturnal boundary layer. The results show that both the length of a stationary TKE signal and the scale of intermittency vary with canopy depth. TKE remains stationary for longer periods above the canopy, and shorter periods are observed in the open space below the live crown. Neutral stability conditions exhibit the highest intermittency at all heights. Additionally a new intermittency factor is introduced which allows for characterizing turbulent regimes. The results have broader implications for understanding and identifying turbulent statistics in the stable boundary layer.