SPECIAL SEMINAR
The dynamics of the Antarctic Circumpolar Current
Richard Karsten
Massachusetts Institute of Technology
10:00 a.m., Wednesday, January 24, 2001
PLEASE NOTE SPECIAL DAY AND TIME
Relaxing the Boussinesq Approximation in Ocean Circulation Models
Richard Greatbatch
Dalhousie University
4:30pm, Thursday, January 25, 2001
No seminar this week
Thursday, February 1, 2001
No seminar this week
Thursday, February 8, 2001
No seminar this week
Thursday, February 15, 2001
No seminar this week
Thursday, February 22, 2001
The tides, they are a changing
Bruce Smith
Mathematics and Statistics Department
Dalhousie University
and
Dave Greenberg
Bedford Institute of Oceanography
4:30pm, Thursday, March 1, 2001
Circulation and mixing in the St. Lawrence Estuary
Daniel Bourgault
McGill University
4:30pm, Thursday, March 8, 2001
A Numerical Model of an Upwelling Event Off the Coast of Nova Scotia
Shawn Donahue
Royal Military College
4:30pm, Thursday, March 15, 2001
The North Atlantic Oscillation
Richard Greatbatch
Department of Oceanography
Dalhousie University
4:30pm, Thursday, March 22, 2001
Title: TBA
Speaker
Institute
4:30pm, Thursday, March 29, 2001
Title: TBA
Speaker
Institute
4:30pm, Thursday, April 5, 2001
Title: TBA
Speaker
Institute
4:30pm, Thursday, April 12, 2001
The Lovelife of North Brazil Current Rings
Markus Jochum
Massachusetts Institute of Technology
4:30pm, Thursday, April 19, 2001
No seminar this week
Thursday, April 26, 2001
Title: TBA
Speaker
Institute
4:30pm, Thursday, May 3, 2001
Sources of Eddy Kinetic Energy in the Labrador Sea
Carsten Eden
Department of Oceanography
Dalhousie University
4:30pm, Thursday, May 10, 2001
Importance of clouds, air temperature and polar vortex to the decaying trend in the Arctic ice cover
Moto Ikeda
(Graduate School of Environmental Earth Science, Hokkaido
University, Sapporo, Japan;
The International Arctic Research
Center/Frontier Research System for Global Change, University of
Alaska, Fairbanks, Alaska, USA;
with
J. Wang and A. P. Makshtas
4:30pm, Thursday, May 17, 2001
Implicit Baroclinic Model for 4D Variational Data Assimilation
Dmitri Nechaev
University of Southern Mississippi
Gleb Panteleev
Memorial University of Newfoundland
4:30pm, Thursday, May 24, 2001
We will present a fully IMPLICIT baroclinic primitive equation model representing the circulation on the time scales greater than the inertial time scales and on spatial scales exceeding the Rossby radius. We do beleave that this model is capable of the baroclinic variational data assimilation for a year-long data sets.
Since the model is intended for data assimilation studies, the forward model was developed simultaneously with the tangent linear and adjoint code. The non-linear forward model utilizes the tangent linear and adjoint code for an efficient solving of the implicit scheme equations on each time step (BiCG technique).
We will discuss the numerical scheme of the model and some preliminary results of data assimilation and simulation of the circulation in the Tsushima Strait and Western Bank regions. The model is controlled via the initial distributions of temperature and salinity, boundary conditions for temperature, salinity and sea surface height on the open boundaries, and sea-surface fluxes.
Title: TBA
Speaker
Institute
4:30pm, Thursday, May 31, 2001
Title: TBA
Speaker
Institute
4:30pm, Thursday, June 5, 2001
Accuracy of Two-Stream Approximations: Tests with a GCM Dataset
Petri Raisanen
Department of Meteorology
University of Helsinki
4:30pm, Thursday, June 14, 2001
In the present study, the accuracy of selected two-stream approximations is quantified using a global GCM-generated dataset (nearly 50 000 atmospheric columns with clouds, aerosols, and absorbing gases), by comparing their results to delta-16-stream reference multiple-scattering calculations. Out of the two-stream methods tested, the Practical improved flux method (PIFM) provided the best results, the delta-Eddington approximation being almost as good. For PIFM, the rms errors in top-of-the-atmosphere and surface net fluxes and in total column solar absorption were only 1.57, 2.18 and 2.11 Wm-2, respectively. However, all two-stream approximations tested had a negative bias of about 1-2 Wm-2 in atmospheric absorption.
In addition to the overall error statistics, the following points will be discussed: (1) how the errors depend on solar elevation?; (2) how large are the errors in the treatment of individual factors such as water clouds, ice clouds, and aerosols?; (3) is it possible to improve the accuracy of two-stream calculations? The ansver to point (3) is in fact positive, in particular, as what comes to the results at low solar elevations.
SPECIAL SEMINAR
The North Atlantic Oscillation: Intraseasonal
Variability and Flow-Dependence
Dr. Thomas Jung
European Centre for Medium-Range Weather Forecasts (ECMWF)
Diagnostics & Predictability Research Section
Shinfield Park, Reading, UK
4:30pm, Thursday, August 30, 2001
Room 5260 (Psychology wing)
The simulated winter NAO variability compares well with the observations. Cross-spectral analysis reveals that the dipole characteristics emerge on time scales longer than 15 days, wheres they are absent on synoptic time scales. On intraseasonal time scales the NAO shows basically a red spectrum. There is little statistical evidence for the presence of significant low-frequency intraseasonal oscillations of the NAO.
The strength of the winter-averaged NAO has a marked effect on the statistical properties of intraseasonal NAO variability. During high NAO winters low-frequency intraseasonal variability of the NAO is less (more) pronounced compared to low NAO winters. It is shown that this asymmetry leaves its imprint on the near-surface temperature response to a forcing by the NAO, particularly over Europe. Finally, the results are discussed in terms of NAO-related changes in medium-range, extended-range, and seasonal atmospheric predictability.