1. VOCALS Update Chris Bretherton, Univ. of Washington

2. VOCALS THEME
To better understand and simulate how marine boundary layer cloud systems surrounding the Americas interact with the coupled ocean-atmosphere-land system on diurnal to interannual timescales.

3. VOCALS in CLIVAR
Bob Weller will assume VOCALS leadership at this meeting.
VPM7 VOCALS participants:
US (Bretherton, Fairall, Mechoso, Weller)
Chile (Garreaud, Ruttland, Pizarro)
Uruguay (Terra – stranded in Uruguay)
Ecuador (Cornejo)
VOCALS observational program overview
VOCALS science advancing understanding/GCM simulation of boundary layer clouds in the coupled climate system.
VOCALS radiator experiment

4. VOCALS Scientific Issues
Time and space scales of CTBL-continent interaction.
Regional S/I feedbacks between Sc clouds, surface winds, upwelling, coastal currents and SST in E Pacific.
Feedbacks of Eastern Pacific cloud topped boundary layer properties on overall tropical circulation and ENSO.
Climatic importance of aerosol-cloud interactions.

5. VOCALS STRATEGIES
Global and mesoscale model evaluation and improvement (e.g parameterization development) using multiscale data sets.
Model sensitivity studies to refine hypotheses and target observations.
Science by synthesis/use of existing data sets, enhancement through targeted instrument procurement, algorithm evaluation and development, and enhanced observation periods.
Co-ordination with oceanographic, aerosol, cloud process communities, including CLIVAR cloud CPT, CLOUDSAT, etc.

6. Ongoing VOCALS observational enhancements:
3.5 years of WHOI stratus buoy (20S 85W) data (Weller)
documents surface met, energy budget, subsurface cooling
by ocean eddies and waves. (SE end of TAO line also useful).
(2) U. Chile installed ceilometer and surface met at San Felix Is.
(maintenance/power continuity issues) (Ruttland/Garreaud).
(3) Buoy maintenance cruises for two weeks every Oct-Nov.
now have PACS-supported NOAA/ETL surface met./
cloud remote sensing (Fairall).
(4) Integrated satellite data:
Nascent JOSS VOCALS archive, starting with GOES data.
Minnis GOES products (selected periods).

7. (Weller)

8. San Felix Island and buoy cloud correlated with southerly coastal jet and clearing. (Garreaud)

9. Clouds in PACS03 at buoy thin compared to the rest of the
cruise (and to EPIC 2001). Lots of aerosol variability
(Fairall/Zuidema)

10. A Patch of Open Cells (POC) MODIS 250m visible imagery
100 km

11. MODIS effective cloud droplet radius – small in coastal pollution
larger in clean areas, excessive in broken cloud of POCs.
large (clean) in drizzle

12. POCs drizzle more
Figure by Kim Comstock/Rob Wood
Can we model apparent local aerosol-cloud-drizzle feedback?

13. Low-latitude cloud feedback Climate Process Team
Goal: Reduce uncertainty in low-latitude cloud feedbacks on climate sensitivity.
In-depth diagnosis of cloud feedbacks in models.
Implement ‘best-practices’ parameterizations honed via single-column methods, newest observations.
Start with boundary-layer clouds, move to deep convective systems.

14. CPT organization
Core group (C. Bretherton, M. Khairoutdinov, C. Lappen, B. Mapes, J. Norris, R. Pincus, B. Stevens, K. Xu, M. Zhang): Parameterization, diagnosis, observational hooks.
Advisory group (B. Albrecht, A. Betts, C. Fairall, T. del Genio, S. Ghan, G. McFarquhar, R. Mechoso, H. Pan, D. Randall, D. Raymond, J. Teixeira, R. Weller)
NCAR–Kiehl, Rasch, Collins; Liaison: hiring underway
GFDL-Klein, Held, Donner; Liaison: Zhao
GMAO-Bacmeister, Suarez.
Not an exclusive effort - active coordination with observational programs such as VOCALS, GCSS, European, Canadian efforts, CFMIP.

15. Annual mean Control run
ERBE
-SWCF
(W m-2)
NCAR
Annual mean Control run
GFDL
GMAO

16. SST+2 Bonygram comparison
NCAR
SST+2 Bonygram comparison
GFDL
GMAO

17. 6-day EPIC buoy period soundings vs. global models
Forecast models and esp. GCMs underestimate ABL depth.
Cloud is too shallow, thin (but surface drizzle still too high).
(Bretherton et al. 2004)

18. Initial conditions (30 levels) at 00Z 16 Oct. 2001
10 K inversion
ESE PBL winds

19. Forcings (from ECMWF analyses)
Homogenize above 600 mb
More subsidence during daytime
Ship-observed
SST = K
Homogenize above 600 mb

20. U. Washington PBL/ShCu schemes in CAM3
Grenier-Bretherton (2001 MWR) moist TKE/explicit entrainment PBL scheme, modified so TKE diagnostic.
Bretherton-McCaa-Grenier (2004 MWR) shallow cu scheme:
- Buoyancy sorting bulk entraining-detraining plume
- Cu-base mass flux
- Plume momentum equation for overshooting entrainment
Single column L30 tests using EPIC dataset (GCSS WG1?)
L30 and L26 tests with T42 Eulerian core using a preliminary version of CAM3.

22. 6-day mean soundings

23. Drizzle suppression sensitivity test

26. Mechoso – UCLA AGCM

27. African topography also promotes Namibian Sc
Mechoso

28. VOCALS ‘radiator-fin’ experiment ca. Oct. 2007?
Transect between WHOI buoy and coast
Goals: Cloud/aerosol interactions, PBL diurnal cycle
mesoscale ocean structure
Diurnal subsidence wave
Cld microphys. gradient
Coastal jet
buoy
Ocn heat transport
3-4 weeks
Surveyed in a radiator pattern by ship (ocn, cld obs)
Aircraft flights along transect
To realize this vision, major S American buy-in needed!