1. CCSM3.5+ Coupled Experiments Rich Neale Phil Rasch, Cecile Hannay, Jon Wolfe, Steve Yeager

2. Experiments 1. The University of Washington (UW) Boundary layer and shallow convection parameterizations 2. 0.5 degree CAM climate projection scoping exercise 3. Development experiments with an additional 20-m thick atmosphere model layer at the surface Results are very preliminary!

3. 1. UW-CCSM3.5  Planentary Boundary Layer (PBL) UW diagnostic TKE scheme (Grenier, Bretherton, Park) replaces existing Holtslag-Boville (HB) scheme UW diagnostic TKE scheme (Grenier, Bretherton, Park) replaces existing Holtslag-Boville (HB) scheme Improved treatment of cloud topped boundary layers Improved treatment of cloud topped boundary layers Stability-based marine stratus calculation removed Stability-based marine stratus calculation removed  Shallow convection (ShCu) UW scheme (McCaa, Bretherton, Grenier) replaces 3- level Hack adjustment scheme UW scheme (McCaa, Bretherton, Grenier) replaces 3- level Hack adjustment scheme Scheme closes on inhibition and TKE from PBL scheme Scheme closes on inhibition and TKE from PBL scheme  UW requires 30 vertical levels compared to 26 for HB (4 extra layers in PBL)

4. Low cloud fraction (%) CAM3.5 Warren annual low cloud CAM3.5 - HBCAM3.5 - UW CAM3.5 - HB error CAM3.5 - UW error Total Difference

5. SW cloud forcing (Wm -2 ) CAM3.5 CERES SWCFCAM3.5 - HB CAM3.5 - UW CAM3.5 - HB error CAM3.5 - UW error Total Difference

6. Low cloud fraction (%) CCSM3.5 Warren annual low cloud CCSM3.5 - UW CAM3.5 - UW CCSM3.5 - UW error CAM3.5 - UW error Total Difference

7. SW cloud forcing (Wm -2 ) CCSM3.5 CERES SWCFCCSM3.5 - UW CAM3.5 - UW CCSM3.5 - UW error CAM3.5 - UW error Total Difference

8. East Pacific SST seasonal cycle HB-CCSM3.5UW-CCSM3.5 HadISST

9. East Pacific SWCF seasonal cycle 5N-5S HB-CCSM3.5UW-CCSM3.5 HadISST

10. HB-CCSM3.5 UW-CCSM3.5 HadiSST ENSO nino3.4 statistics Note different scales Events peak in February

11. ENSO teleconnections Nino3 SSTA lag-0 correlation HB-CCSM3.5 UW-CCSM3.5 HadISST

12. Competitive coupled climate Competitive coupled climate Taylor Diagram Metrics Radial direction – variance Angle - correlation UW-CCSM3.5 HB-CCSM3.5

13. 2. High-Res CAM – CCSM3.5  CCSM advisory board encouraged high resolution short-term ‘climate projections’  AIM: Provide greater detail on shorter timescales (a couple of decades) before GHG emission scenarios diverge significantly  0.5 degree atmosphere with 1 deg (nominal) ocean  Maintain 2 degree physics timestep (30 minutes)  1980-2000 initial spin-up period (done)  Greenhouse gas + aerosol forcings  2001-2030 projection period (to do)

14. Benefits of higher resolution

15. Rainfall (DJF)

16. Rainfall (JJA)

17. Asian Monsoon + ITCZ GPCP Rainfall mm/day (JJA) 2 degree0.5 degree 2 degree0.5 degree GPCP Monsoon rainfall focused closer to orography Twin ITCZ remains

18. East Pacific SST seasonal cycle 5N-5S 2 degree0.5 degree HadISST

19. Surface Stress 5N-5S 2 degree minus ERS stress 0.5 degree minus ERS stress

20. ENSO nino3 SSTA statistics (1980-1999) 2 degree 0.5 degree

21. 2 deg HadISST ENSO teleconnections Nino3 SSTA lag-0 correlation 0.5 deg

22. 3. 20-m layer CAM – CCSM3.5  20-m thick layer next to the surface  Leads to improved surface flux calculations  Surface flux averaging required to stabilize simulation and to use same CAM timestep 20m

23. GPCP Rainfall (JJA) mm/day HB-CAM3.520m-CAM3.5 West Pacific Rainfall

24. East Pacific SST seasonal cycle 5N-5S HB-CCSM3.520m-CCSM3.5 HadISST

25. 20m-CCSM3.5 UW-CCSM3.5 HadiSST ENSO nino3.4 statistics Note different scales

26. Summary  UW CCSM3.5 UW scheme provides improved moist PBL (cloud-topped) UW scheme provides improved moist PBL (cloud-topped) Inclusion of UW PBL-ShCu scheme gives a stable coupled climate Inclusion of UW PBL-ShCu scheme gives a stable coupled climate More favorable SCu location; excessive SWCF More favorable SCu location; excessive SWCF East Pacific SST semi-annual -> annual cycle shift East Pacific SST semi-annual -> annual cycle shift ENSO period 4-7 years; excessive amplitude ENSO period 4-7 years; excessive amplitude  High Resolution CAM CCSM3.5 Short-term/high resolution climate projection scoping exercise Short-term/high resolution climate projection scoping exercise Improved North American mean climate Improved North American mean climate Better defined monsoonal features; twin ITCZ remains Better defined monsoonal features; twin ITCZ remains East Pacific SST semi-annual -> annual cycle shift East Pacific SST semi-annual -> annual cycle shift ENSO characteristics maintained from lower resolution ENSO characteristics maintained from lower resolution  20-m thick layer CAM CCSM3.5 Improved representation of surface stability/flux characteristics Improved representation of surface stability/flux characteristics Significant changes in mean climate Significant changes in mean climate Favorable location shift; excessive seasonal cycle Favorable location shift; excessive seasonal cycle East Pacific SST semi-annual -> annual cycle shift East Pacific SST semi-annual -> annual cycle shift ENSO period >4 years; weak amplitude ENSO period >4 years; weak amplitude  Preliminary results!