Overview of the CCSM CCSM Software Engineering Group June

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

atm ocn ice lnd Coupler datm (cycling climate data) CAM2 AGCM dlnd CLM docn (cycling SST data) POP OGCM dice CSIM CCSM Components

CCSM Component Models Atmosphere: NCAR CAM2 –T42 26 levels –1-D decomposition (64pe limit) –Improved Dynamics, Radiation and Parameterizations Ocean: Parallel Ocean Program (POP1.4.3) –~1 degree horizontal grid –40 levels –2-D data decomposition

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

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

Current CCSM2 Runs Control (600 years) 1%/year CO2 increase Constant 2x CO2 Control with T85 atm

High Resolution Atmosphere Simulation

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. Climate Models

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. Climate Model

Model Climate = Real Climate!!! Model Equilibrium Time X Real Climate Model Climate Steady State SolutionAdjustment

Climate Change Processes Rate of change & variance should be equal Climate Change Process Time X Real Climate Model Climate AE

CCSM is considered to be a solid model by the scientific community

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

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

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