2017 CMS Winter Meeting

Waterloo, December 8 - 11, 2017

Abstracts        

Environmental and Geophysical Fluid Dynamics
Org: Kevin Lamb, Francis Poulin and Marek Stastna (University of Waterloo)

TRIANTAPHYLLOS AKYLAS, Massachesetts Institute of Technology

PETER BARTELLO, McGill University

NICHOLAS GRISOUARD, University of Toronto

NAKAYAM KEISUKE, Kobe University

NICHOLAS KEVLAHAN, McMaster University

KEVIN LAMB, University of Waterloo

ADAM MONAHAN, University of Victoria
Regime Dynamics of the Stably Stratified Atmospheric Boundary Layer  [PDF]

Flow, stratification, and turbulence in the atmospheric boundary layer are dynamically coupled: turbulent intensity and fluxes are influenced by the character of the eddy-averaged state, which in turn is itself influenced by the turbulent fluxes. This interplay is of particular interest in the stably stratified atmospheric boundary layer, which is observationally found to exist in distinct regimes. The first, the weakly stable boundary layer (wSBL), is characterized by weak bulk shear, a modest inversion, and sustained turbulence. The second, the very stable boundary layer (vSBL), has strong bulk shear, a strong inversion, and turbulence which is weak and intermittent.

This talk will present recent observational and idealized modelling results regarding these regimes and the transitions between them. First, the regimes will be separated in data using a Hidden Markov Model (HMM) analysis of long time series of tower observations. Idealized physical models will then be used to elucidate the physical mechanism resulting in these regimes. Equilibrium and linear stability analyses will be presented and compared with time-dependent model behaviour. Finally, these ideas will be combined in a stochastic model of the bulk boundary layer momentum budget which provides a physically-based, if idealized, model for the probability distribution of near-surface winds.

DAVID MURAKI, Simon Fraser University

FRANCIS POULIN, University of Waterloo

MAREK STASTNA, University of Waterloo

DAVID STRAUB, McGill University

BRUCE SUTHERLAND, University of Alberta

MIKE WAITE, University of Waterloo

Sponsors

Centre de recherches mathématiques Pacific Institute for the Mathematical Sciences Fields Institute AARMS: Atlantic Association for Research in the Mathematical Sciences University of Waterloo

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