1. Climate Dynamics 11:670:461 Alan Robock robock@envsci.rutgers.edu
Lecture 15, 10/28/13
Climate Dynamics 11:670:461
Alan Robock
Department of Environmental Sciences
Rutgers University, New Brunswick, New Jersey USA

4. Evolution of processes included in state-of-the-art climate models
FAR: First IPCC Assessment Report
SAR: Second Report
TAR: Third Report
AR4: Fourth Report
IPCC AR4, Chapter 1

6. IPCC AR4, Chapter 1

9. General Circulation Models (GCMs) 1
Basic Physical Laws:
Conservation of energy (First law of thermodynamics)
Conservation of momentum (Newton’s second law of motion)
Conservation of mass (Continuity equation)
Conservation of moisture
Hydrostatic equilibrium
Gas law

10. General Circulation Models (GCMs) 2
Physical Processes That Must or Can Be Included:
Wind Sea ice
Radiation Snow
Precipitation Glaciers
Soil moisture Vegetation
Ground water Ocean biota
Aerosols
Clouds, convective and large-scale
Air-sea exchanges of moisture, energy, and momentum
Air-land exchanges of moisture, energy, and momentum
Chemistry, particularly O3 and CO2
Ocean temperature, salinity, and currents

11. Real World vs. Model World

12. Theory of Climate Model Development Actual Climate Model Development
How to Construct a Climate Model
Programmatic
objectives
Management
directives
Preconceived
notions
Incorrect interpretation
of observations
Code
errors
Unrealistic
assumptions
Further
misunderstanding
Further refinement of
unimportant details
Publication
Coincidental agreement
between theory
and observations
Confusion
Sophisticated
computer model
Theoretical
Sparse and
infrequent
observations
Actual Climate Model Development

13. Typical grid spacing of a GCM is now 1° x 1° latitude- longitude by 1 km in the vertical.
Each time the horizontal resolution is increased by a factor of 2, the time needed to run the model goes up by a factor of 8.
When the vertical resolution is doubled the time required doubles in general, but can go up by more, if winds become faster.

14. To include all the processes in a climate model which are of a scale smaller than is resolved by the model, they must be “parameterized.”
One of the most important and difficult climate elements to parameterize is cloudiness. Clouds have a much smaller spatial and temporal scale than a typical GCM grid box.
Usually, we consider separately 2 types of clouds, layer clouds and convective clouds. There is no fundamental prognostic equation for clouds (no conservation of clouds principle); rather they form when condensation takes place and dissipate due to precipitation and evaporation.

15. Rows and flows of angel hair
And ice cream castles in the air
And feather canyons everywhere;
I’ve looked at clouds that way.
But now they only block the sun.
They rain and they snow on everyone.
So many things I would have done
But clouds got in my way.
I’ve looked at clouds from both sides now.
From up and down, and still somehow
It’s cloud illusions I recall.
I really don't know clouds at all.
— Joni Mitchell
Both Sides Now, 1967