VOCALSChris Bretherton, Univ. of Washington

Bob Weller, WHOI

VOCALS GOALVOCALS GOAL

Better understand, simulate, and predict the Southeast Pacific cool-ocean climate regime and its interactions with

the larger-scale coupled ocean-atmosphere-land system on diurnal to

interannual timescales.

VOCALS in CLIVAR• VOCALS is a process study developed within VAMOS.• VOCALS conceived in EPIC planning as follow-on to

EPIC 2001 stratus pilot cruise, then refined in WG meetings at VPM3-7 (2000-2004) and Corvallis (2004).

• VOCALS research elements informally began in 2003, to continue until 2010.

• VOCALS has strong US and international participation:US (Albrecht, Bretherton, Cronin, Fairall, Huebert, Mechoso, McWilliams, Samelson, B. Stevens, S.-P. Xie, Weller, Wood)Chile (Garreaud, Ruttland, Pisarro, Nunez)Uruguay (Terra)Ecuador (Cornejo)

• Draft science and implementation plans: www.atmos.washington.edu/~breth

UCAR/JOSS site: www.joss.ucar.edu/vocals/

Central cool-ocean concerns

• Regulation of SST• Cloud-topped

boundary layers

Why CLIVAR needs VOCALS

• Low-latitude cool-ocean regions are a major error source in coupled climate models that affect the entire tropical circulation, including mean, seasonal cycle, and ENSO.

• They are important places to study the aerosol indirect effect and cloud-aerosol interactions.

• The SEP is a good place, scientifically and logistically, on which to focus new resources.

E Pacific SST biases in CCSM3

• Warm SST bias in SE Pac, NE Pac, NE Atl.• Spurious semiannual cycle in SEP SST.• Biennial ENSO.• SEP parameterization errors contributes to these

problems, but how much? Errors in both coastal-zone upwelling and offshore processes contribute.

CCSM3 shortwave cloud radiative forcing

• Diverse SWCF errors across SEP (anemic stratus region, bright trade cu), only partly explaining SST biases.

• Other models have similar skill level.

Cloud feedbacks on ENSO

• The cool-ocean regime is important for ENSO– Sets mean state at E end of equatorial waveguide– Feedbacks between SST, clouds, radiation, circulation

JAS surface CRF [W m-2] regressed on ENSO

Park and Leovy 2005

LessLow cloud

More deepconvection

Both

Cloud-aerosol feedbacks and indirect effect

POCs

Manifest in POCs (pockets of open cells)?

Bretherton et al (2004)

POCS, cloud droplet size, and drizzle

Rob WoodSandy Yuter

Why go to the SEP when California is

closer? • SEP cool region

extends to equator, interacts with ENSO, has most persistent low clouds.

• SEP has research-grade buoys and strategic islands.

• Exploit SEP/NEP geographical/aerosol contrasts.

• Strong international partners, particularly in Chile.

VOCALS Science Issues

…based on what we have learned from EPIC, other SEP observations and modeling studies:

• Atmospheric, oceanic, and coupled model biases and model improvement in the SEP and other subtropical cool-ocean regimes.

• SEP aerosol-cloud interaction; implications for aerosol indirect effect and regional climate.

• SST distribution and the ocean heat/tracer budgets in the SEP.

• Role of South America and remote forcing from tropics and midlatitudes, on diurnal to interannual (ENSO) timescales.

SEP model errors still important!

EPIC2001ECMWFNCEPAM2.10CAM2.0

Bretherton et al. (2004) Yu and Mechoso (2001)

Aerosol variability is dramatic

Nov. 2003 PACS cruise

20S 85 W

Kollias et al. (2004)

New particle production

A daily gravity wave initiated by Andean slope heating enhances the diurnal cycle of cloud out to 1500 km offshore.

18LT06LT

Garreaud and Munoz (2004) – 21 day regional MM5 simulation

12LT06LT00LT

Oceanic heat divergence

2001 2002 2003

• Annual-mean heat flux into ocean ~ 30 W m-2 at 1500 km offshore under persistent low cloud!

(20S 85W)

Why? …not Ekman fluxes.Upwelling also inadequate.

Weller

Weller

Do upwelling-initiated westward propagating Rossby waves/eddies ‘ventilate’ the SEP?

S-P Xie

VOCALSVOCALS IMPLEMENTATIONIMPLEMENTATION• Global and mesoscale model evaluation and

improvement (e.g parameterization development) using multiscale data sets, sensitivity studies, and refined understanding of relevant physical processes.

• Observational synthesis of existing data sets (e.g. buoy, satellite, reanalysis) and targeted measurement enhancements.

• ‘Radiator Fin’ IOP in October 2007: detailed observations of SEP aerosol, clouds, ocean processes.

• Co-ordination with oceanographic, aerosol, cloud process communities, including CLIVAR cloud CPT (NCAR/GFDL), IGBP/SOLAS, NOAA Climate Testbed (NCEP), ARM, Cloudsat, GCSS, etc.

VOCALS TimelineVOCALS Timeline2003-2010

Diagnostic/modeling work ETL-enhanced cruisesSFI met stationVOCALS data archive

2005-2007CloudSat/CalypsoSpin up regional ocean modelingInitiate TAO radiation obs?

2007-2010Preparation/analysis for Oct. 07. VOCALS-RF IOP.

Buoy maintenance cruise enhancements

• Take advantage of two+ week WHOI stratus buoy maintenance cruise required each fall.

• ETL PACS-funded since 2003 to deploy EPIC-Sc like surface flux, cloud remote sensing, sondes, as well as limited aerosol measurements on these cruises. – Good way to test new shipboard measurement

approaches– Builds up a ‘climatology’.– Samples other parts of SEP on way.– Could do hi-res XBT, other enhanced ocean sectioning.– 2003 and 2004 cruises successful, with interesting new

observations each time

• Inadequate funding for analyzing results fully. Organized VOCALS funding could enhance our investment by allowing trajectory analysis, better model comparison, etc.

TAO enhancements

• For EPIC, LW/SW radiation sensors deployed on TAO 95 W buoys.

• Would be nice VOCALS addition to put radiation measurements on TAO buoys at 0-8S, 95-125 W– ENSO-interactive region– Ground truth for ISCCP-FD surface radiation retrievals.– Allows ocean heat budget computation in this region– Cronin (PMEL) would be prepared to implement/analyze

data.– Instrumentation relatively cheap ($100-200K) and

piggybacks on existing telemetry/data archival system

Satellite studies (MODIS, CloudSat, Calypso)

• MODIS retrieval biases.

• CloudSat/Calypso 2005-2007+ excellent comparison for clouds, aerosols, maybe drizzle.– 2007 IOP probably in time for ground truth.– R. Wood actively involved.

MODIS effective cloud droplet radius seems excessive in broken cloud of POCs. Can we do better?

large (clean) in drizzle

Can CloudSat to detect Sc drizzle and its horizontal variability, e.g. POCs?

Kim Comstock/Rob Wood fromStevens et al. (2005).

Atmospheric/coupled modeling

Actively represented in VOCALS…but could bettercoordinate strategy, data use with more funding,.• Coupled GCMs

- CCSM (U. Washington/NCAR)- UCLA (Mechoso)

• Regional models- IPRC RegCM (S.-P. Xie)- U Chile MM5 (Garreaud)- COAMPS-ROMS (Oregon St./UCLA)

• LES/single column modeling- U. Washington (SCAM+LES), UCLA (LES)

• Also CPT, GCSS, ARM-CAPT, NOAA Climate Testbed.

Regional Ocean

Modeling• Appropriate

framework for understanding small-scale ocean processes and heat budgets.

• VOCALS will spin up for SEP (McWilliams, Samelson, Large).

• More comparison with global ocean models needed.

• 2007 IOP is a tailor-made comparison for ROMs.

(McWilliams)

VOCALS Radiator Fin Experiment

• October 2007 – month long field campaign• Aircraft: C-130 (endurance,payload)

aerosonde (daily surveys, POC tracking)• Ship: Ronald H Brown (C-band radar, clouds)

Wecoma (mesoscale SeaSoar survey)• San Felix Island: ARM Mobile Facility?• Satellites: Coordinate with overpasses as feasible.• Chilean coast: surface measurements/soundings• S American-led coastal-zone IOP.• Near-real time atmospheric mesoscale modeling.

Goal: In-situ measurements of aerosols, cloud microphysics, and ocean mixing processes/heat fluxes 0-1200 km offshore.

1. What factors influence drizzle formation and POCs? Is aerosol the critical factor?

2. What are the aerosol characteristics, sources and sinks in both the coastal and remote SEP?

3. What is the vertical structure of SEP mesoscale ocean eddies/waves. Do their lateral heat fluxes dominate ocean heat divergence in non-coastal SEP? Ditto for tracers. Can ROMs reproduce eddy/SST/tracer

structure? 4. Do the phase speed and vertical structure of the

Andean diurnal subsidence wave match model predictions?

5. Do satellite and ship-based retrievals of aerosol, cloud drop radius and drizzle agree with in-situ observations?

VOCALS-RF motivating questions (distilled)

VOCALS-RF Study Region

West-East cross-section

Measurement Platform

Coverage/sampling Main science goals

AIRCRAFT:1. NSF NCAR C-

1302. Unmanned

Aeronautical Vehicle (UAV)

(a) Cross sectional flights between Arica (Chile) and either the IMET Buoy or San Felix Island (Figs 4.1 and 4.3)(b) Lagrangian-type flights to follow and map out POCs and surrounding stratocumulus (Fig 4.4)

Cloud-aerosol-drizzle interactions

Aerosol characterization, sources/nucleation

MBL and cloud structure between the S American coast and the remote SEP

SHIP 1:NOAA R/V Ronald H

Brown(ship)

Stationary measurement periods at three locations along the 20S parallel (75, 80 and 85W) and another at a location to be specified depending upon the mesoscale oceanic eddy activity.

Cloud-aerosol-drizzle interactions

MBL structural properties and energy/moisure budgets

Ocean heat transport, SST and ocean current mapping

Diurnal cycle of MBL and free-troposphere

SHIP 2:UNOLS R/V Wecoma

class

“Radiator fin” pattern from 20oS,75oW and sampling between 75oW and 85oW, 20oS and 27oS for 18 days, and 1.25ox1.25o butterfly pattern centered at the WHOI/IMET buoy for 6 days.Conduct mesoscale survey near 22oS, 80oW in collaboration with RHB (5 days)

Mesoscale hydrographic, optical, small-scale mixing and velocity structure under the stratus deck.

Lateral transports and the role of oceanic mesoscale eddies

Mesoscale and eddy variability of nutrient transport/aerosol precursor emissions

Mesoscale coupling between SST and cloud variability

Third ship(S American)

Coastal sampling pattern to study near-coastal oceanic upwelling, coastal meteorology, aerosol

and aerosol precursor (DMS) production.

Coastal upwelling propertiesAerosol precursor distribution

San Felix Island(80W, 27S) Fixed location sampling of aerosol, cloud, and

drizzle properties using the ARM Mobile Facility (AMF) for 3 month period around field program.Aerosol sampling [Fairall+others]

Cloud-aerosol-drizzle interactionsPOCs structure and initiationAerosol sources/sinks in the remote SEP

IMET Buoy(85W, 20S)

Fixed location, surface sampling of MBL properties, radiation, SST, ocean currents (Fig 4.1)

Daily to interannual variability of SST, cloud and MBL properties. Ocean heat transport

Coastal Chile/Peru TBD Coastal meteorology and cloud cover

VOCALS-RF measurements

Measurement Platform

Coverage/sampling Main science goals

AIRCRAFT:1. NSF NCAR

C-1302. Unmanned Aeronautical Vehicle (UAV)

(a) Cross sectional flights between Arica (Chile) and either the IMET Buoy or San Felix Island (Figs 4.1 and 4.3)(b) Lagrangian-type flights to follow and map out POCs and surrounding stratocumulus (Fig 4.4)

Cloud-aerosol-drizzle interactionsAerosol characterization, sources/nucleationMBL and cloud structure between the S American coast and the remote SEP

SHIP 1:NOAA R/V Ronald H

Brown(ship)

Stationary measurement periods at three locations along the 20S parallel (75, 80 and 85W) and another at a location to be specified depending upon the mesoscale oceanic eddy activity.

Cloud-aerosol-drizzle interactionsMBL structural properties and energy/moisure budgetsOcean heat transport, SST and ocean current mappingDiurnal cycle of MBL and free-troposphere

SHIP 2:UNOLS R/V

Wecoma class

“Radiator fin” pattern from 20oS,75oW and sampling between 75oW and 85oW, 20oS and 27oS for 18 days, and 1.25ox1.25o butterfly pattern centered at the WHOI/IMET buoy for 6 days.Conduct mesoscale survey near 22oS, 80oW in collaboration with RHB (5 days)

Mesoscale hydrographic, optical, small-scale mixing and velocity structure under the stratus deck.Lateral transports and the role of oceanic mesoscale eddiesMesoscale and eddy variability of nutrient transport/aerosol precursor emissionsMesoscale coupling between SST and cloud variability

Third ship(S American)

Coastal sampling pattern to study

near-coastal oceanic upwelling, coastal

meteorology, aerosol and aerosol

precursor (DMS) production.

Coastal upwelling propertiesAerosol precursor distribution

San Felix Island

(80W, 27S)

Fixed location sampling of aerosol, cloud, and drizzle properties using the ARM Mobile Facility (AMF) for 3 month period around field program.Aerosol sampling [Fairall+others]

Cloud-aerosol-drizzle interactionsPOCs structure and initiationAerosol sources/sinks in the remote SEP

IMET Buoy(85W, 20S) Fixed location,

surface sampling of MBL properties, radiation, SST, ocean currents (Fig 4.1)

Daily to interannual variability of SST, cloud and MBL properties. Ocean heat transport

Coastal Chile/Peru

TBD Coastal meteorology and cloud cover

Flight pattern 1: Cross-section

Flight pattern 2: POC drift

Conclusions

• VOCALS is an integrated process study effectively blending modelers and observationalists.

• Modeling and data gathering/synthesis activities are ongoing but only loosely organized, needs targeted VOCALS funding to be effective.

• VOCALS Radiator Fin experiment proposed for Oct. 2007. Pushback would risk CloudSat/Calipso coordination. Many platforms ‘free’, but likely requires at least $5M (including analysis) funding for 2007-2010.

• We are scientifically and technically ready to proceed and succeed.