12.804 Large-scale Flow Dynamics Lab

Fall 2005

Animated tropopause maps at 12 hour intervals during the Blizzard of 2003, a typical "northeaster" with record breaking snowfall for Boston. Tropopause maps such as these are an analysis of potential temperature (color contours) on a surface of constant potential vorticity, Q (Q = 2.0 PVU). This analysis contains the essential information needed to understand the dynamics of weather systems within the troposphere. "Cold" tropopause (i.e. low potential temperature) regions are associated with cyclonic circulations, while "warm" tropopause regions are associated with anti-cyclonic circulations. (Image by Dr. Lodovica Illari.)

Course Highlights

This course features projects and background material in the readings section.

Course Description

12.804 is a laboratory accompaniment to 12.803, Quasi-balanced Circulations in Oceans and Atmospheres. The subject includes analysis of observations of oceanic and atmospheric quasi-balanced flows, computational models, and rotating tank experiments. Student projects illustrate the basic principles of potential vorticity conservation and inversion, Rossby wave propagation, baroclinic instability, and the behavior of isolated vortices.

Syllabus

Overview

This is a laboratory course intended to illustrate the concepts presented in 12.803. We will analyze observations of oceanic and atmospheric quasi-balanced flows, computational models, and rotating tank experiments. The projects will illustrate the basic principles of potential vorticity conservation and inversion, Rossby wave propagation, baroclinic instability and the behavior of isolated vortices.

Concepts

Geostrophic Adjustment
1. Response to Initial Conditions
2. Response to Slow Forcing
Quasi-geostrophic Balance
1. Validity of Geostrophic Approximation
2. Corrections
Invertability and Superposition Principles
1. 2D Inversion
2. 3D Inversion
3. Superposition
Rossby Waves and Frontal Waves
1. Forced Rossby Waves
2. Waves on a PV Front, Comparison to Rossby Waves
3. Nonlinear Dynamics, Rossby Wave Instabilities
Higher Order Balance
Baroclinic Instability
1. Linear Growth
2. Nonlinear Dynamics - Secondary Instability, PV Fluxes
Ageostrophic Motion

Prerequisite

Fluid Dynamics of the Atmosphere and Ocean (12.800)

Corequisite

Quasi-balanced Circulations in Oceans and Atmospheres (12.803)

Grading

Grading is based on lab writeups and presentations.

Calendar

For each topic, students have the choice of a few different projects, each with a different method/data set. Generally, the options are: Numerical Modeling, Tank Modeling, Ocean Data, and Atmospheric Data. On the first day of each unit the instructors introduce the projects and students divide into groups. Most sessions, the students work in groups during classtime with help from the instructors.

Course schedule.
SES #	TOPICS
1	Introduction, Geostrophic Balance Projects Introduced
2-4	Geostrophic Balance In-class Work
5	Geostrophic Balance Presentations
6	Vortex Interaction Projects Introduced
7-8	Vortex Interaction In-class Work
9	Vortex Interaction Presentations
10	Geostrophic Adjustment Projects Introduced
11-12	Geostrophic Adjustment In-class Work
13	Geostrophic Adjustment Presentations
14	Rossby Waves and Quasi-geostrophic Projects Introduced
15-17	Rossby Waves In-class Work
18	Rossby Waves and Quasi-geostrophic Presentations
19	Frontal Waves Projects Introduced
20-22	Frontal Waves In-class Work
23	Frontal Waves Presentations
24	Baroclinic Instability Projects Introduced
25	Baroclinic Instability In-class Work
26	Baroclinic Instability Presentations