Geophysical Fluid Dynamics and Physical Oceanography.
Office: Burnside Hall 819
Tel.: (514) 398-8995
Fax.: (514) 398-6115
david.straub [at] mcgill.ca (E-mail)
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Research interests
Our research concentrates on geophysical fluid dynamics (GFD) applied to the ocean circulation. Particular interests have included abyssal circulation, Southern Ocean dynamics, thermobaricity, interannual variability in ocean circulation, and energetics of large scale (balanced) flow. The last of these is described in more detail below.
Models of ocean circulation invariably include parameterisations of unresolved processes. One approach in modelling is to tune the relevant coefficients (within reasonable limits) in a way that gives the best possible fit to observed data. Ultimately, however, this is unsatisfactory since it makes the science non-deductive. There has been a recent interest, therefore, in the sensitivity of simple models (especially of the wind driven circulation) to the precise values of tunable parameters. What one hopes is that the statistics of the solution become insensitive to eddy viscosities and the like in the limit that these become small (or, equivalently, as the Reynolds number becomes large). Unfortunately, this has not proved to be the case.
Part of my research has related this to energetics and in particular, to the reverse cascade of geostrophic turbulence. We argue that model convergence in the limit of all dissipation parameters should be expected only if i) the wind power input goes to zero or ii) there is a transfer of energy from geostrophic modes to (forward cascading) ageostrophic modes. (We are exploring both possibilities.) We have shown that the wind stress acting on the ocean surface is (albeit weakly) dependent on the surface ocean velocity. In model simulations, accounting for this dependence reduces the power source by about 35%. Most of this is associated with a midlatitude jet. Also shown is a snapshot of the vorticity forcing. At large scales, forcing is cyclonic in the northern half of the domain and anticyclonic in the southern half. At smaller scales, the forcing is intimately linked to the surface currents themselves.
Some recent publications
- Trossman, D., B. Arbic, D. Straub, J. Richman, E. Chassinet and A. Wallcraft, 2017. The role of rough topography in mediating impacts of bottom drag in eddying ocean circulation models. J. Phys. Oceanogr., Vol. 47. #8, pp. 1941-1959.
- Asselin, O., P. Bartello and D.N. Straub, 2017. On Boussinesq dynamics near the Stropopause. under review, J. Atmos. Sci.. (online in 2017 in print in 2018)
For a complete list of publications, please visit our publications page.