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VOCALS Update Chris Bretherton, Univ. of Washington. 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. . VOCALS in CLIVAR.

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Vocals update chris bretherton univ of washington
VOCALS UpdateChris Bretherton, Univ. of Washington

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.

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)

    Ecuador (Cornejo)

  • VOCALS observational program overview

  • VOCALS science advancing understanding/GCM simulation of boundary layer clouds in the coupled climate system.

  • VOCALS radiator experiment

Vocals scientific issues
VOCALSScientific Issues

  • Time and space scales of CTBL-continent interaction.

  • Regional S/I feedbacks between Sc clouds, surface winds, upwelling, coastal currentsand 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.

Vocals update chris bretherton univ of washington


  • 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.

Vocals update chris bretherton univ of washington

  • 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).

A patch of open cells poc modis 250m visible imagery


A Patch of Open Cells (POC)MODIS 250m visible imagery

Pocs drizzle more
POCs drizzle more

Figure by Kim Comstock/Rob Wood

Vocals update chris bretherton univ of washington

MODIS effective cloud droplet radius – small in coastal pollution

larger in clean areas, excessive in broken cloud of POCs.

large (clean) in drizzle

Low latitude cloud feedback climate process team
Low-latitude cloud feedback Climate Process Team pollution

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.

Cpt organization
CPT organization pollution

  • 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.

Annual mean control run

ERBE pollution

Annual meanControl run


(W m-2)




Sst 2 bonygram comparison

NCAR pollution




6 day epic buoy period soundings vs global models
6-day EPIC buoy period soundings vs. global models pollution

  • Forecast models and esp. GCMs underestimate ABL depth.

  • Cloud is too shallow, thin (but surface drizzle still too high).

Initial conditions 30 levels at 00z 16 oct
Initial conditions (30 levels) at 00Z 16 Oct. pollution

10 K inversion

ESE PBL winds

Forcings from ecmwf analyses
Forcings (from ECMWF analyses) pollution

Homogenize above 600 mb

More subsidence during daytime


SST = 291.8 K

Homogenize above 600 mb

U washington pbl shcu schemes in cam3

U. Washington PBL/ShCu schemes in CAM3 pollution

  • 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.

Vocals update chris bretherton univ of washington

Diurnal subsidence wave

Cld microphys. gradient

Coastal jet


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!