VOCALS Chris Bretherton, Univ. of Washington Bob Weller, WHOI

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VOCALSChris Bretherton, Univ. of WashingtonBob
Weller, WHOI
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VOCALS 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.
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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/

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Central cool-ocean concerns

• Regulation of SST
• Cloud-topped boundary layers

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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.

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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.

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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.

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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
Both
More deep convection
Less Low cloud
Park and Leovy 2005
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Cloud-aerosol feedbacks and indirect effect
Manifest in POCs (pockets of open cells)?
POCs
Bretherton et al (2004)
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POCS, cloud droplet size, and drizzle
Rob Wood Sandy Yuter
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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.

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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.

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SEP model errors still important!
EPIC2001 ECMWF NCEP AM2.10 CAM2.0
Yu and Mechoso (2001)
Bretherton et al. (2004)
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Aerosol variability is dramatic
Nov. 2003 PACS cruise
20S 85 W
New particle production
Kollias et al. (2004)
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A daily gravity wave initiated by Andean slope
heating enhances the diurnal cycle of cloud out
to 1500 km offshore.
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Oceanic heat divergence
(20S 85W)
2003
Weller
2002
2001

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

Why? not Ekman fluxes. Upwelling also inadequate.
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Do upwelling-initiated westward propagating
Rossby waves/eddies ventilate the SEP?
S-P Xie
Weller
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VOCALS IMPLEMENTATION

• 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.

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VOCALS Timeline
2003-2010 Diagnostic/modeling work
ETL-enhanced cruises SFI met station VOCALS data
archive 2005-2007 CloudSat/Calypso Spin up
regional ocean modeling Initiate TAO radiation
obs? 2007-2010 Preparation/analysis for Oct. 07.
VOCALS-RF IOP.

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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.

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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

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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.

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MODIS effective cloud droplet radius seems
excessive in broken cloud of POCs. Can we do
better?
large (clean) in drizzle
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Can CloudSat to detect Sc drizzle and its
horizontal variability, e.g. POCs?
Kim Comstock/Rob Wood from Stevens et al. (2005).
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Atmospheric/coupled modeling

• Actively represented in VOCALSbut could better
• coordinate 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 (SCAMLES), UCLA (LES)
• Also CPT, GCSS, ARM-CAPT, NOAA Climate Testbed.

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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)
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VOCALS Radiator Fin Experiment
Goal In-situ measurements of aerosols, cloud
microphysics, and ocean mixing processes/heat
fluxes 0-1200 km offshore.

• 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.

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VOCALS-RF motivating questions (distilled)

• 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?

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VOCALS-RF Study Region
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West-East cross-section
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VOCALS-RF measurements
Measurement Platform Coverage/sampling Main science goals
AIRCRAFT NSF NCAR C-130 2. 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 properties Aerosol 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 Fairallothers Cloud-aerosol-drizzle interactions POCs structure and initiation Aerosol 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
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Measurement Platform Coverage/sampling Main science goals
AIRCRAFT 1. NSF NCAR C-130 2. 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 properties Aerosol 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 Fairallothers Cloud-aerosol-drizzle interactions POCs structure and initiation Aerosol 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
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Flight pattern 1 Cross-section
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Flight pattern 2 POC drift
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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.