Lecture outlines for GCC Summer School, 7-13 May, 2005

Lecture outlines for GCC Summer School

Dr. Richard Rood
NASA Goddard

Lectures 1, 2, and 3

Prof. Dylan Jones
Department of Physics
University of Toronto

Prof. Adam Sobel
Department of Applied Physics and Applied Mathematics
Columbia University

1D Radiative-convective Models:
- Formulation:
  - thermodynamic equations
  - parameterizations
- Uses:
  - Global mean climate theory
  - parameterization
  - single column dynamics
- Forcing methods:
  - Radiative-convective equilibrium
  - imposed advective tendencies
  - "weak temperature gradient" and other recent developments
  - Strengths and weaknesses of each approach
- Examples & comparisons to observations
Models with reduced vertical structure:
- Derivation
  - Layers (isentropic, etc.)
  - Levels
  - Modes: linear analysis with a rigid lid
  - Interpretation of modal derivation given vertical propagation of atmospheric waves
  - Modes: convective quasi-equilibrium derivation
- Single-layer/single-mode models: Applications
  - Stratospheric polar vortex/surf zone
  - Tropical dynamics: Gill model, monsoons, ENSO?
- Two-layer/two-mode models: Applications
  - Baroclinic instability
  - Quasi-equilibrium tropical circulation model
- Three-layer hurricane models.
Cloud-resolving models:
- Dynamics: nonhydrostatic, anelastic vs. compressible
- Boundary conditions
- Physics: cloud microphysics, radiation, subgridscale turbulence
- Applications:
  - Short-timescale weather events
  - long-timescale, climate-relevant simulations
- Examples, comparisons to observations, pretty pictures

Dr. Markus Rex
Alfred Wegener Institute for Polar and Marine Research, Potsdam

Chemical equations and kinetics
- Dynamics of chemical reaction systems (the behaviour of the
- Typical systems of differential equations)
- Transient and steady state solutions
- The concept of "lifetime" of species
- Typical behaviour of chemical systems under a
- Periodic forcing (e.g. seasonal cycles, daily variations)
Box models
- Relevant species in the stratosphere
- The concept of chemical families
- The families HO_x, NO_y/NO_x, Cl_y/ClO_x, including
- Examples from the "real atmosphere"
Polar chemistry studies
- Use of box models of different complexity to test our
- Understanding of polar ozone loss
- Match observations versus box model results
- Climate change and polar ozone loss: models versus observations

Dr. Charles McLandress
Department of Physics
University of Toronto

Tidal Models
- Observational motivation:
  - UARS satellite results
- Background theory:
  - terminology
  - linear disturbances on the sphere
- Middle atmosphere GCM simulations:
  - comparison of simulated tides to observations
  - forcing mechanisms in the troposphere and middle atmosphere
- Uses of linear mechanistic models:
  - model set up
  - dissipation in the mesosphere
  - interpretation of GCM results
Planetary Wave Models
- Quasi-stationary planetary waves:
  - observational motivation
  - Charney-Drazin theory
  - 1D versus 2D linear models
  - 3D nonlinear models
- Travelling planetary waves (the 2-day wave):
  - observational motivation
  - some background theory
  - middle atmosphere GCM simulations
  - 3D nonlinear models
Gravity Waves in GCMs
- Resolved gravity waves:
  - forcing mechanisms
  - spectral characteristics in the middle atmosphere
  - implications for transport
- Unresolved gravity waves:
  - overview of the parameterization problem
  - role in generating the quasi-biennial oscillation
- Comparisons to observations

Prof. Paul Kushner
Department of Physics
University of Toronto

Lecture 1: 3-D Models of the Extratropical General Circulation
- Our every day weather in midlatitudes (baroclinic eddies) can be captured qualitatively by very simple layer and continuous 3-D models derived from scaling arguments and linearization.
- The very simple model phenomena are also seen in 3-d nonlinear (dry) GCM simulations with simple physics.
- The behaviour of these 3-d models gives us a key to understanding the midlatitude general circulation: the way baroclinic eddies transport heat and tracers out of the subtropics to high latitudes, determine tropopause structure (references to Tapio's work), and play a key role in strat-trop coupling (Scinocca-Haynes and my work with Lorenzo). This behaviour is robust across a wide range of parameters. So, in principle, we could tune a simple GCM to look like observations.
- But it is not enough to fit a simple 3-d model to obs if we want to make *quantitative* comparisons with nature. So we need to get to work build more accurate and sophisticated models ...
Lecture 2: Building General Circulation Models
- We have made the case that we need an accurate and sophisticated model to make quantitative comparisons with nature. What this implies about the physical, dynamical, and transport components of the model.
- How might we go about building a GCM? Choosing a dynamical core and a parameterization package. Getting locked in to a model.
- Putting the pieces together and comparing with observations.
- Some personal experiences with GCM building.
Lecture 3: Using General Circulation Models
- In Lecture 2, we started comparing GCMs to nature. What are some appropriate strategies for doing this?
- The world of MIPs (Model Intercomparison Projects). Some strengths and weaknesses of current GCMs and of MIPs themselves.
- Strategies for evaluating GCM forecasts of climate change: robust and non-robust responses.
- Final remarks: how Isaac Held's ideas on bridging the gap between simulatiing and understanding climate tie into this workshop.

Dr. Anne Douglass
NASA Goddard

Lagrangian Models
- Lagrangian Model - trajectory code + photochemical code
- Initialization
- Applications
  - interpretation of aircraft data
  - interpretation of satellite data
  - inverse modeling
Numerical Transport schemes
- Performance criteria
- Basics of shock capturing schemes
- Performance
  - Lin and Rood 1996
  - Prather 2nd order moments
  - resolution - importance to polar processes
Chemical transport models
- Development history
  - why off-line
  - assimilated winds
- Successes with assimilated winds 1990 - 2004
- Problems with assimilated winds for transport
  - symptoms
  - strategies to ameliorate (isentropic models)
  - long-standing problems
    - age of air
    - flux of ozone (etc.) to the troposphere
- Performance metrics based on satellite observations