1. CCSM AMWG Meeting June 25, 2003 Status of CAM Bill Collins and Leo Donner National Center for Atmospheric Research and Geophysical Fluid Dynamics Laboratory Model biases in CAM2 Creation of CAM2.X Physics and dynamics proposed for CAM 2.X ⁻ Integrated physics package ⁻ Simulated climate ⁻ Effects of new physics on model biases

2. CCSM AMWG Meeting June 25, 2003 AMWG Agenda

3. CCSM AMWG Meeting June 25, 2003 Ongoing Development of CAM CAM 2.0.2 Spring 2003 CAM 2.X Major changes to physics, code structure CCSM 2.2 Integration “Late” Spring 2003 CCSM X, CAM3 Physics adjustments, dycore decision Fall 2003

4. CCSM AMWG Meeting June 25, 2003 Main Model Biases in CAM2/CCSM2 http://www.cgd.ucar.edu/cms/mstevens/amwg/experiments.html http://www.cgd.ucar.edu/cms/mstevens/amwg/experiments.html Overestimation of winter land surface temperatures  Bias largely eliminated in CAM 2.X Underestimation of tropical tropopause temperatures  Bias reduced in CAM 2.X Double ITCZ and extended cold tongue  Double ITCZ mitigated in CAM 2.X Erroneous cloud response to SST changes  Signs and pattern of response corrected in CAM 2.X Errors in E. Pacific surface energy budget  Overestimation of insolation larger in CAM 2.X Underestimation of tropical variability  Underestimation still present

5. CCSM AMWG Meeting June 25, 2003 Winter Land Surface Temperatures CAM 2CAM 2.X

6. CCSM AMWG Meeting June 25, 2003 Tropical Tropopause Temperatures CAM 2CAM 2.X

7. CCSM AMWG Meeting June 25, 2003 Tropical Precipitation CAM 2CAM 2.X CAM 2.X - CAM 2

8. CCSM AMWG Meeting June 25, 2003 Cloud Forcing during Warm-Cold Events CAM 2CAM 2.XERBE

9. CCSM AMWG Meeting June 25, 2003 E. Pacific Surface Energy Budget Net SW Net LWLatent Heat Flux

10. CCSM AMWG Meeting June 25, 2003 E. Pacific Cloud Properties Cloud FractionCloud Optical Depth

11. CCSM AMWG Meeting June 25, 2003 Surface Stresses CAM 2 CAM 2.X - CAM2

12. CCSM AMWG Meeting June 25, 2003 MJO Variability CAM 2.X NCEP

13. CCSM AMWG Meeting June 25, 2003 New Physics in CAM 2.X Relative to CAM 2 http://www.ccsm.ucar.edu/working_groups/ipcc2003changes.htm http://www.ccsm.ucar.edu/working_groups/ipcc2003changes.htm Clouds and condensate:Clouds and condensate: –Improved prognostic cloud water & moist processes –Transfer of mixed phase precipitation to land surface –Improved cloud parameterization Radiation:Radiation: –Shortwave forcing by diagnostic aerosols –Updated SW scheme for H 2 O absorption –Updated LW scheme for LW absorption and emission Surface models:Surface models: –Introduction of CLM 2.2 –Reintroduction of Slab Ocean Model (SOM) Energy fixers for dynamics + diagnosticsEnergy fixers for dynamics + diagnostics

14. CCSM AMWG Meeting June 25, 2003 Other Changes in CAM 2.X Updated boundary data sets –Navy  USGS orography –NOAA  new PCMDI ozone New diagnostics –ISCCP cloud simulator Software improvements –Update to CPL 6 –Performance enhancements to SLD, FV dycores

15. CCSM AMWG Meeting June 25, 2003 Increased Cloud Condensate Separate cloud liquid and ice variables Advect cloud condensate Include latent heat of fusion Use ice & water variables for cloud optics New dependence on temperature for cirrus particle size Sedimentation of cloud droplets and ice particles Modified evaporation of rain CAM 2CAM 2.X CAM 2.X – CAM 2

16. CCSM AMWG Meeting June 25, 2003 Increased Cloud Amounts PBL height constrained Rain rate > 0 Convection cloud amounts from convective mass fluxes Stratocumulus clouds in lowest 2 levels Changes to autoconversion thresholds Changes to relative humidity thresholds Fall speed of droplets is function of effective radius  NET TOA =  4.5 Wm  2 NET TOA = 0.53 Wm  2 CAM 2CAM 2.X CAM 2.X – CAM 2

17. CCSM AMWG Meeting June 25, 2003 Changes in Cloud Amounts New – Old Cloud Parameterization

18. CCSM AMWG Meeting June 25, 2003 Reduction in Net Surface Flux (Effects of Increased Cloud Amounts) New – Old Cloud Parameterization

19. CCSM AMWG Meeting June 25, 2003 Changes in Temperature and Humidity (Effects of Increased Cloud Amounts) New – Old Cloud Parameterization

20. CCSM AMWG Meeting June 25, 2003 Addition of Prescribed Aerosol Forcing

21. CCSM AMWG Meeting June 25, 2003 Changes in Longwave Cooling Rates: New H2O Lines and Continuum Change in LBL Cooling Change in CAM Cooling

22. CCSM AMWG Meeting June 25, 2003 Dipole Changes in LW Cooling Rates

23. CCSM AMWG Meeting June 25, 2003 Global Decrease in Longwave Fluxes

24. CCSM AMWG Meeting June 25, 2003 Changes in Shortwave Heating Rates: New H2O Lines and Continuum LBL Heating CAM2 Heating CAM2x Heating Tropics

25. CCSM AMWG Meeting June 25, 2003 Global Increase in SW Heating Rates

26. CCSM AMWG Meeting June 25, 2003 Global Decrease in Surface Insolation

27. CCSM AMWG Meeting June 25, 2003 Acknowledgements The senior scientists of CMS, for their work and dedication to create CAM 2.X Jim McCaa and Tom Henderson, for their tireless efforts to build the next versions of CAM The Software Engineers of CMS, for their ongoing support of the climate model Andrew Conley, David Fillmore, and Julia Lee-Taylor, for their development of new radiation schemes Mark Stevens, for producing a steady stream of diagnostics to guide the development effort Tony Craig, for integrating CAM into CCSM The AMWG, for contributing new physics, dynamics, and diagnostics, and applications for CAM

28. CCSM AMWG Meeting June 25, 2003 The Near Future Next steps for FV: –AMIP-style integration –Parallel Eulerian and FV integrations of CCSM –Decision by WGs and SSC later this summer Higher resolution versions of CAM needed: –T85 and T170 equivalent for IPCC –Issue: will physics scale to higher resolution? –Issue: release of higher resolution to AMWG Release of new CAM & CCSM to AMWG – dates? Vectorization – SSC has provisionally endorsed

29. CCSM AMWG Meeting June 25, 2003 Conclusions A new version of CAM has been developed. Several critical biases have been reduced: –Winter land surface temperature error –Response of SW cloud forcing to tropical SST –Underestimate of tropopause temperatures –Double ITCZ Several critical biases remain: –Underestimate of intraseasonal variability –Errors in surface fluxes and stress in E. Pacific Challenges for next generation CAM: –Convection –Cloud/radiation interactions –Incorporation of atmospheric chemistry –“Your issue here”