Our group meets weekly (or so) on Tuesdays for an informal seminar or discussion group at 1pm in room 3B of the Mathematical Institute. All are welcome.
Seminars for 2014-2015
- 7 October 2014: Dr. Yue-Kin Tsang from
the University of Edinburgh, "Advection-condensation of water vapour in a model of coherent stirring"
Water vapour is an important greenhouse gas whose distribution has a strong impact on climate. We study the dynamics of atmospheric moisture using an advection-condensation model. The transport of moist parcels is modelled as a large-scale circulating motion with small-scale Brownian fluctuation. Condensation of moisture occurs when the specific humidity of a parcel exceeds a prescribed local saturation value. We consider both the initial-value and the steady-state problem of this stochastic model and derive the probability distribution of the moisture field. Theoretical predictions are verified by Monte Carlo simulations.
Seminars for 2013-2014
- 1 April 2014: Chuong Van Tran "The growth of velocity norms in Navier-Stokes flows"
- 25 March 2014: Dr. Dan Lucas from
University College Dublin, "Recurrent flows embedded in 2D turbulence"
The so called "dynamical systems approach" has seen great success in recent years in investigating transitional and weakly turbulent flows. This approach sees such flows as a trajectory through a phase space littered with invariant ('exact') solutions and their stable and unstable manifolds. It is therefore natural to ask whether any ideas attempting to rationalise chaos may have something to say about developed turbulence. With this in mind, long-time simulations of body-forced turbulence on a 2D torus are presented with the purpose of extracting simple invariant sets or 'exact recurrent flows'. Each recurrent flow represents a sustained closed cycle of dynamical processes which underpins the turbulence. These are used to reconstruct the turbulence statistics in the spirit of Periodic Orbit Theory. We also explore several new examples of this technique by exploring new localised states in extended spatial domains, attracting and transient chaos, and show some preliminary results from three-dimensional turbulence.
- 18 March 2014: No meeting
- 11 March 2014: David Dritschel "Dynamics and statistics of point vortices on a sphere"
- 4 March 2014: No meeting
- 25 February 2014: Richard Scott "A self-similar cascade of filament instabilities in the surface quasigeostrophic system"
- 18 February 2014: No meeting
- 11 February 2014: Stuart King "Advanced computational methods for stratified flows"
- 4 February 2014: No meeting
- 28 January 2014: No meeting
- 21 January 2014: Dr. Stefanella Boatto from UFRJ Brazil, "The N-body, the N-vortices and N-charges dynamics on surfaces: a common view point"
- 14 January 2014: Dr. Xavier Perrot from LMD Paris, "Atmospheric response to sea-surface temperature mesoscale structures"
- Christmas Break...
- 10 December 2013: Dr. Will McKiver
from CMCC Italy,
"Impact of mesoscale dynamics on global marine plankton models"
Here we examine the impact of resolving mesoscale processes on the global marine biogeochemical plankton system by performing simulations at two different resolutions, 2 degree (LO-res) and 1/4 degree resolution (HI-res) using the PELAGOS model. Both the LO-res and HI-res simulations are set up with the same forcings and biogeochemical parameterizations, while the initial conditions are provided by a spinup of the LO-res simulation. This allows us to perform a direct inter-comparison of the two cases with a view to understanding how the introduction of mesoscale features affects the biogeochemical system, specifically how differences in the resolved horizontal and vertical motions are reflected in the plankton biomass and the nutrient availability. While the global large-scale oceanographic features (fronts, gyres, etc) are captured in both the LO-res and HI-res simulations, differences in the mesoscale flow structures, and in particular the resolved vertical physics in the HI-res simulation generate very different behaviour in the biogeochemical system. These differences in the physics drives what is a spun-up biogeochemical system in the LO-res simulation into a new regime in the HI-res simulation with significant reduction of typical low resolution biases.
- 3 December 2013: No meeting
- 26 November 2013: Chuong Van Tran, "Regularity for the 3D Navier-Stokes equations"
- 19 November 2013: Prof. Marcel Oliver from Jacobs University,
- Mid-term break...
- 29 October 2013: David Dritschel "On the limitations of balance" continued...
- 22 October 2013: David Dritschel: "On the limitations of balance"
- 15 October 2013: Greg King "Meanders through sea-surface winds" continued...
- 8 October 2013: Greg King "Meanders through sea-surface winds"
- 1 October 2013: Discussion of topics raised by Greg King
- 24 September 2013: Discussion of group website