Fall 2001

Barotropic Waves Generated by Rapidly Moving Storms

Doug Mercer, Jinyu Sheng, Richard Greatbatch, and Josko Bobanovic

Environment Canada
Newfoundland Weather Centre, Gander

4:30 p.m., Thursday, September 27, 2001


Danish Efforts Of Modelling The Waters Around Greenland

Nicolai Kliem

Bedford Institute of Oceanography

4:30pm, Thursday, October 4, 2001

Abstract: The efforts made at the Danish Meteorological Institute to model the ocean circulation and the drift of sea ice in the waters around Greenland will be presented. The main objective of the study was originally to be able to predict sea ice drift in the waters around Greenland 2-3 days in advance, with the ocean modelling serving as forcing for a sea ice model. Though, the Ocean modeling has received increasingly priority with participation in a study of drift of shrimp larvae. Emphasis has mainly been on the area around Cape Farewell as well as the West-Greenland waters.

The presentation will start with the efforts of modelling the ocean current off Cape Farewell, following by the ideas for simulating the Labrador Sea and Baffin Bay.

Second part of the presentation will be on the drift of sea ice in the Cape Farewell area. During the study a sea ice model was developed and is in the process of being applied for operational forecasts. The forecasting system will be described. The model is a relatively simple drift model. Results from the validation highlight the most important limitations of the model, and provides directions for further development.

Influence of curved coastlines on an idealized shallow water free-slip ocean and the inertial runaway problem

Frederic Dupont

Bedford Institute of Oceanography

4:30pm, Thursday, October 11, 2001

Abstract: We used a spectral element shallow water model for investigating the "inertial runaway problem" in irregular domains for the single-gyre Munk problem. Ideally, one would like the statistical equilibrium observed at large Reynolds number to be insensitive to model choices that are not well founded, e.g., the precise value of the viscous coefficient, and choice of dynamic boundary condition. Simple models of geophysical flows are indeed very sensitive to these choices. For example, flows typically converge to unrealisticly strong circulations, particularly under free-slip boundary conditions, even at rather modest Reynolds numbers. This is referred to as the "inertial runaway problem". We showed that the addition of irregular coastlines to the canonical problem helps to slow considerably the circulation, but does not prevent runway.

Observing Internal Waves with a Digital Camera

Daniel Bourgault

Department of Oceanography
Dalhousie University

4:30pm, Thursday, October 18, 2001

Abstract: In the summer of 2000 I experimented with the use of a digital camera to observe the sea-surface signature of high-frequency internal gravity waves. Internal waves could be clearly identified from areal photographs as propagating bands of slightly different sea-surface roughness. After refinements this method could provide an interesting mean to evaluate the direction of propagation, the phase speed, and wavelength of internal waves.

Weak Constraint Parameter Estimation in Ecosystem Modeling

Svetlana Loza

Department of Oceanography
Dalhousie University

4:30pm, Thursday, October 25, 2001


Seasonal Nudging of Deep Ocean and Shelf Models

Keith Thompson

Department of Oceanmography
Dalhousie University

4:30pm, Thursday, November 1, 2001


A Model of the North Atlantic with Assimilation of Hydrographic Data

Dan Wright

Bedford Institute of Oceanography

4:30pm, Thursday, November 8, 2001


A Brief History of Edge Waves

A.J. Bowen and S. Henderson

Department of Oceanography
Dalhousie University

4:30pm, Thursday, November 15, 2001
Please Note: Room LSC 3655


Flow through penetrable roughness: large-eddy simulation of forest aerodynamics

Roger Shaw

University of California, Davis

4:30pm, Thursday, November 22, 2001

Abstract: The surface layer is the lowest portion of the atmospheric boundary layer in direct contact with the underlying surface and whose properties are determined by exchanges at that surface. Simple schemes are sometimes sufficient to parameterize such transfer processes (using roughness lengths, transfer coefficients etc.) but it is often necessary, and always scientifically interesting, to examine how the atmosphere interacts with a vertically distributed array of sources and sinks.

We choose as our example, a forest canopy and examine the distinct changes in aerodynamic processes that occur at the interface with the overlying atmosphere, and within the air spaces of the stand. Most obviously, the branches, leaves and trunks of trees act as a blockage to the flow, diminishing internal wind speeds. More interesting is the presence of elevated wind shear at treetop height and a mixing layer that results in much greater organization to canopy turbulence than is found over smoother surfaces. The array of canopy elements, which have dimensions smaller than the energy containing eddies, acts to accelerate the dissipation process and diminish turbulence levels. Finally, pressure perturbations created in the shear zone and imposed on flow deep inside a forest canopy dominate the structure of turbulence at that level.

This presentation examines these topics within the framework of a large-eddy simulation of atmospheric surface layer flow that includes air layers within a canopy such as a forest.

The Dynamics of the Barotropic Tides in the Korea/Tsushima Strait

Jeff Book

U.S. Naval Research Laboratory, Stennis Space Center

4:30pm, Thursday, November 29, 2001


Special Seminar
Arctic sea ice variability and associated surface freshwater fluxes in the northern North Atlantic

Peter Lemke

Bremerhaven, Germany

1:30 pm, Friday, November 30, 2001
Room 4258, Psychology Bldg.
Note Special day, time, and location

Abstract: High latitudes have received attention recently because of significant changes in the atmosphere - sea ice - ocean system. The surface air temperature in the Arctic has increased by 1.1oC over the last 50 years, i.e. more than three times as fast as the global air temperature, which increased by 0.6oC over 100 years. The Arctic sea ice extent in spring and summer decreased by 10% since the 1950s, and it was reported that the sea ice thickness during late summer declined by about 40% since 1958. A warming is also observed in the Arctic Ocean at intermediate depths. These amplified trends are in agreement with warming scenarios performed with coupled climate models, which indicate an amplified response in high latitudes to increased greenhouse gas concentrations. But details of the complex interaction between atmosphere, sea ice and ocean are still only marginally known.

In this presentation the optimisation of sea ice models and an application to 50 years of NCEP/NCAR atmospheric forcing will be discussed, with special emphasis on the long-term variability of sea ice extent, thickness and export to the North Atlantic.

Modeling the physical environment effects on the early life stages of fish and invertebrates in the Gulf of St. Lawrence

Joel Chasse

Bedford Institute of Oceanography

4:30pm, Thursday, Deceember 6, 2001


A simple model of the circulation in a baroclinic ocean with topography

Carsten Eden

Department of Oceanography
Dalhousie University

4:30pm, Thursday, December 13, 2001

Merry Christmas!!!
See you in January...