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

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

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  1. VOCALSChris Bretherton, Univ. of WashingtonBob Weller, WHOI

  2. 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.

  3. 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/

  4. Central cool-ocean concerns • Regulation of SST • Cloud-topped boundary layers

  5. 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.

  6. 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.

  7. 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.

  8. 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

  9. Cloud-aerosol feedbacks and indirect effect Manifest in POCs (pockets of open cells)? POCs Bretherton et al (2004)

  10. POCS, cloud droplet size, and drizzle Rob Wood Sandy Yuter

  11. 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.

  12. 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.

  13. SEP model errors still important! EPIC2001 ECMWF NCEP AM2.10 CAM2.0 Yu and Mechoso (2001) Bretherton et al. (2004)

  14. Aerosol variability is dramatic Nov. 2003 PACS cruise 20S 85 W New particle production Kollias et al. (2004)

  15. 00LT 06LT 12LT 18LT 06LT Garreaud and Munoz (2004) – 21 day regional MM5 simulation A daily gravity wave initiated by Andean slope heating enhances the diurnal cycle of cloud out to 1500 km offshore.

  16. 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.

  17. Do upwelling-initiated westward propagating Rossby waves/eddies ‘ventilate’ the SEP? S-P Xie Weller

  18. VOCALSIMPLEMENTATION • 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.

  19. 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.

  20. 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.

  21. 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

  22. 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.

  23. MODIS effective cloud droplet radius seems excessive in broken cloud of POCs. Can we do better? large (clean) in drizzle

  24. Can CloudSat to detect Sc drizzle and its horizontal variability, e.g. POCs? Kim Comstock/Rob Wood from Stevens et al. (2005).

  25. Atmospheric/coupled modeling Actively represented in VOCALS…but 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 (SCAM+LES), UCLA (LES) • Also CPT, GCSS, ARM-CAPT, NOAA Climate Testbed.

  26. 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)

  27. 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.

  28. 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?

  29. VOCALS-RF Study Region

  30. West-East cross-section

  31. VOCALS-RF measurements

  32. Flight pattern 1: Cross-section

  33. Flight pattern 2: POC drift

  34. 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.

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