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Overview of the CCSM CCSM Software Engineering Group [email protected] June 29 2002 www.ccsm.ucar.edu What is CCSM? CCSM is a coupled climate model for simulating the earths climate system. www.ccsm.ucar.edu CCSM Components CAM2 AGCM atm datm (cycling climate data) CLM lnd dlnd Coupler docn (cycling SST data) ocn POP OGCM www.ccsm.ucar.edu dice CSIM ice 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 www.ccsm.ucar.edu 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 www.ccsm.ucar.edu 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 www.ccsm.ucar.edu Current CCSM2 Runs • Control (600 years) • 1%/year CO2 increase • Constant 2x CO2 • Control with T85 atm www.ccsm.ucar.edu High Resolution Atmosphere Simulation www.ccsm.ucar.edu 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. www.ccsm.ucar.edu 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. www.ccsm.ucar.edu Model Equilibrium Model Climate = Real Climate!!! Real Climate Model Climate X Adjustment Steady State Solution Time www.ccsm.ucar.edu Climate Change Processes Rate of change & variance should be equal Real Climate X Model Climate A E Climate Change Process Time www.ccsm.ucar.edu 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 Significant collaborations with: – US university community – US Department of Energy (DOE) • LANL, LLNL, LANL, ORNL, ANL, LBL, NERSC – National Air and Space Administration (NASA) www.ccsm.ucar.edu 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 www.ccsm.ucar.edu 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 [email protected] www.ccsm.ucar.edu