Temperature statistics above a deepocean sloping boundary
Cimatoribus, A.A.; van Haren, H. (2015). Temperature statistics above a deepocean sloping boundary. J. Fluid Mech. 775: 415435. dx.doi.org/10.1017/jfm.2015.295
In: Journal of Fluid Mechanics. Cambridge University Press: London. ISSN 00221120; eISSN 14697645, meer
 
Author keywords 
geophysical and geological flows; internal waves; stratified turbulence 
Auteurs   Top 
 Cimatoribus, A.A., meer
 van Haren, H., meer



Abstract 
We present a detailed analysis of temperature statistics in an oceanographic observational dataset. The data are collected using a moored array of thermistors, $100~\text{m}$100 m tall and starting $5~\text{m}$5 m above the bottom, deployed during four months above the slopes of a Seamount in the northeastern Atlantic Ocean. Turbulence at this location is strongly affected by the semidiurnal tidal wave. Mean stratification is stable in the entire dataset. We compute structure functions, of order up to 10, of the distributions of temperature increments. Strong intermittency is observed, in particular, during the downslope phase of the tide, and farther from the solid bottom. In the lower half of the mooring during the upslope phase, the temperature statistics are consistent with those of a passive scalar. In the upper half of the mooring, the temperature statistics deviate from those of a passive scalar, and evidence of turbulent convective activity is found. The downslope phase is generally thought to be more sheardominated, but our results suggest on the other hand that convective activity is present. Highorder moments also show that the turbulence scaling behaviour breaks at a welldefined scale (of the order of the buoyancy length scale), which is however dependent on the flow state (tidal phase, height above the bottom). At larger scales, wave motions are dominant. We suggest that our results could provide an important reference for laboratory and numerical studies of mixing in geophysical flows. 
