The cessation of continuous turbulence as precursor of the very stable nocturnal boundary layer

The cessation of continuous turbulence as precursor of the very stable nocturnal boundary layer

Van de Wiel, B.J.H.
Moene, A.F.
Jonker, H.J.J.

Applied Sciences

Multi-Scale Physics

2012-11-01

The mechanism behind the collapse of turbulence in the evening as a precursor to the onset of the very stable boundary layer is investigated. To this end a cooled, pressure-driven flow is investigated by means of a local similarity model. Simulations reveal a temporary collapse of turbulence whenever the surface heat extraction, expressed in its nondimensional form h/L, exceeds a critical value. As any temporary reduction of turbulent friction is followed by flow acceleration, the long-term state is unconditionally turbulent. In contrast, the temporary cessation of turbulence, which may actually last for several hours in the nocturnal boundary layer, can be understood from the fact that the time scale for boundary layer diffusion is much smaller than the time scale for flow acceleration. This limits the available momentum that can be used for downward heat transport. In case the surface heat extraction exceeds the so-called maximum sustainable heat flux (MSHF), the near-surface inversion rapidly increases. Finally, turbulent activity is largely suppressed by the intense density stratification that supports the emergence of a different, calmer boundary layer regime.

atmosphere-land interaction
heat budgets/fluxes
small scale processes
stability
surface fluxes
nonlinear models

http://resolver.tudelft.nl/uuid:bff4c9dc-21d5-40dd-8073-2f7859f4b13d

https://doi.org/10.1175/JAS-D-12-064.1

American Meteorological Society

2013-05-01

1520-0469

http://journals.ametsoc.org/doi/abs/10.1175/JAS-D-12-064.1

Journal of the Atmospheric Sciences, 69 (11), 2012

Institutional Repository

journal article

(c) 2012 American Meteorological Society