Overview of the CCSM

1
Overview of the CCSM
CCSM Software Engineering Group
csm_at_ucar.edu June 29 2002
2
What is CCSM?

• CCSM is a coupled climate model for simulating
  the earths climate system.

3
CCSM Components
4
CCSM Component Models

• Atmosphere NCAR CAM2
• T42 26 levels
• 1-D decomposition (64pe limit)
• Improved Dynamics, Radiation and Parameterizati
  ons
• Ocean Parallel Ocean Program (POP1.4.3)
• 1 degree horizontal grid
• 40 levels
• 2-D data decomposition

5
CCSM Component Models

• Sea-Ice CSIM4
• Elastic-viscous-plastic (EVP) dynamics, ice
  thickness distribution energy conserving
  thermodynamics
• High/Low resolutions on POP grids
• Land Community Land Model (CLM2)
• Global Land surface model
• 10 vertical soil layers, 128x64 horizontal points
• 16 different vegetated types
• Surface hydrology and river runoff

6
Previous CSM1 and PCM Simulations

• greenhouse gas and sulfate aerosol forcing
• 1870 control simulation
• Historical 1870 to present
• IPCC Business as Usual assumption
• IPCC stabilization assumption
• Multi-member ensembles
• Solar variability simulation-ensemble of 4

7
Current CCSM2 Runs

• Control (600 years)
• 1/year CO2 increase
• Constant 2x CO2
• Control with T85 atm

8
High Resolution Atmosphere Simulation
9
Climate Models
Expense and work involved with climate
predictions and the pretty pictures that
result adds an aura of truth to climate model
output Don't be fooled. Climate models are
only sophisticated tools, not crystal balls.
10
Climate Model
Given the size of the problem and the finite
amount of computer power that can be brought to
bear, compromises have to be made.   Some
important physical processes cannot be
represented explicitly. They must be represented
approximately by numerical parameterizations.  
Parameterizations are approximations and are not
exact. Different parameterizations produce some
of the differences in the simulations of
different climate models.
11
Model Equilibrium
Model Climate Real Climate!!!
12
Climate Change Processes
13
CCSM is considered to be a solid model by the
scientific community
14
Distributed Involvement

• CCSM is a large community project
• NSF / National Center for Atmospheric Research
• Significant collaborations with
• US university community
• US Department of Energy (DOE)
• LANL, LLNL, LANL, ORNL, ANL, LBL, NERSC
• National Air and Space Administration (NASA)

15
CCSM Working Groups

• Scientific development via working groups
• Atmosphere Model
• Ocean Model
• Land Surface
• Polar Model
• Climate Variability
• Paleoclimate
• Biogeochemistry
• Climate Change and Assessment
• Software Engineering
• Annual CCSM Workshop in Breckenridge Colorado

16
How can you get involved?

• Take part in the CCSM working groups
• Feel free to change the code for your own uses,
  but be sure to validate your science
• Don't be afraid to debug problems yourself
• Take advantage of your local sysadmins and NCAR
  consultants to fix problems
• If the problem is clearly with the model, check
  the known bugs area CCSM Forum, then contact
  ccsm_at_ucar.edu