Improving understanding, model simulations, and prediction of the Southeast Pacific Climate System

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• Improving understanding, model simulations, and
  prediction of the Southeast Pacific Climate
  System

Field Program
Regional pollution
Mesoscale ocean eddies
Stratocumulus clouds
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The Southeast Pacific Climate

• Cold SSTs, coastal upwelling
• Cloud-topped ABLs
• Influenced by and influential on remote
  climates (ENSO)
• Unresolved issues in heat and nutrient budgets
• Important links between clouds and aerosol
• Poorly simulated by atmosphere-ocean GCMs

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Logistical slides/Agency
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VOCALS Science Working Group

• Roberto Mechoso, UCLA, USA (chair)
• Chris Bretherton, Univ of Washington, Seattle,
  USA
• Chris Fairall,  NOAA/ESRL, Boulder, USA
• Barry Huebert, Univ of Hawaii at Manoa, USA
• Jim McWilliams, UCLA, USA
• Oscar Pizarro, U Concepción, Chile
• José Rutllant, U Chile, Santiago, Chile
• Bob Weller, WHOI. Woods Hole USA
• Hemantha Wijesekera , Oregon State Univ., USA
• Robert Wood, Univ of Washington, Seattle, USA
• Shang-Ping Xie, IPRC, Univ of Hawaii, USA
• Carlos Ereño, Int'l CLIVAR
• José Meitín (ex officio), NCAR EOL/VAMOS Office

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VOCALS Timeline
IUGG Perugia
Planning Phase
VOCALS REx
VOCALS Conference
Field site surveys
REx and Modeling Workshops
2003 - 2006
2007
2008
2009
2010
Field and modeling synthesis/analysis
PI Proposal submission
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THE VOCALS STRATEGY
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IGBPs Surface Ocean Lower Atmosphere Study
(SOLAS) has formally agreed to collaborate with
CLIVAR on VOCALS. http//www.uea.ac.uk/env/sola
s/
In the remote marine atmosphere the supply of DMS
and its oxidation mechanisms limit the rates of
new particle nucleation and growth. These
processes probably control the re-filling of POCs
with clouds. Iodine, ammonia, and organics may
also play a role. SOLAS proposes to study this
chemistry from both ships and aircraft.
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Model problems
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Cloud feedbacks

• Agreement between models is worst for Sc regions
• GCMs disagree even on the sign of low-cloud
  feedback.

Red high-sensitivity models Blue
low-sensitivity models from Bony Dufresne
(2005)
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Clouds in climate models- change in low cloud
amount for 2?CO2
GFDL
CCM
model number
from Stephens (2005)
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Clouds in Global ModelsAnnual meanControl
runAtmospheric models
-SWCF (W m-2)
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CGCM Problems NOAA CFS Model
CFS Errors

• The CFS model has significant errors in the SEP
• There is a meridional shift in ITCZ (top), a
  warm SST bias (middle) and insufficient
  stratocumulus cloud cover, (bottom)
• These errors adversely affect the skill of CFS
  climate forecasts (ENSO).
• What model developments are required to alleviate
  these errors?

Prec
SST
CLD
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UCLA-AGCM globally coupled to MIT-OGCM High-atmosp
heric resolution (2.5X2)
Simulated annual mean SST
Observed annual mean SST
Cold tongue is asymmetric relative to the
Equator. Equatorial West-East SST gradient is
realistic. Double ITCZ in both Pacific and
Atlantic Oceans still exist, but SST errors are
smaller.
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SST Biases in Coupled Models

• SST Biases in NCAR CCSM (Collins et al. 2006)

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Role of stratus on double ITCZ bias
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Why this Uncertainty?
Free-tropospheric T set by ITCZ
12K!
?e
2,000km
1km
BL T set by local SST
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Aerosol-Cloud-Precipitation
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The effect of low clouds on climate
SST
Stratus Cloud Amount (Warren)
Net CRF
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Sep-Novlow cloud amount(EECRA)
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Drizzle is important over the SEP
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Mesoscale variability in stratocumulus
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Aerosol issues in SEP
VOLCANOES

• Locations and strengths of sources of natural and
  anthropogenic aerosols and precursors
• Regional distribution of aerosol. Relative
  contribution of anthropogenic and natural sources
  
• Effects of aerosol on micro and macrophysical
  cloud properties

SMELTERS
DUST
DMS
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Global cloud droplet concentration (MODIS, annual
mean 2001-2004)
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Cloud Microphysical Variability
Smelter locations
MODIS Cloud Droplet Concentration (SON
2001-2004)
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Pockets of Open Cells (POCs)
200 km
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Importance of POCs

• Open cell coverage can be significant
• Strong intraseasonal variability
• Association with drizzle

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EPIC data, Bretherton et al. (2004)
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POCs and drizzle
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Aerosol speciation over the SEP
D0.05 mm
Tomlinson et al. (2007)
Ammonium Bisulfate
Sulfuric Acid
D0.2 mm
50 100 150 200 250
Temperature C
Results indicate that submicron aerosol is
predominantly composed of a mixture of sulfuric
acid and ammonium bisulfate
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Aerosol, cloud, drizzle and POCs
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POCs and Aerosols

• Strong reductions in accumulation mode aerosol
  concentration
• New nucleation
• Links between aerosol microphysics and cloud
  macrophysics?

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POC formation
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The POC breeding grounds
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Coverage of open cells, LWP/Nd from MODIS
(MODIS)
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Mesoscale stratocumulus structure
Open Cells
Closed Cells
Satellite

• Cloud albedo
• strongly dependent upon open/closed cells
• Strong precipitation associated with open cell
  structure
• Open cells form in clear marine environment
  potential anthropogenic impacts

Low albedo
High albedo
Ship Radar
Strong drizzle
Weak drizzle
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Satellite issues
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MODIS VIS/NIR Retrievals Problematic
Liquid water path
Effective radius
Cloud drop conc.
open cells
closed cells
MODIS 10/19/2001 1000 Local (1600 UTC)
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CloudSat observes drizzle
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Oceanography issues
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Mesoscale ocean eddies

• Mesoscale ocean eddies form in coastal upwelling
  regions and propagate westward
• Their impact on the heat, nutrient, and
  freshwater budgets is poorly known
• They are not resolved in coupled GCMS

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Mesoscale ocean eddies
Height
SST

• Eddies impact SST and can be observed using
  altimetry

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Upper Ocean heat budgets that do not close
(20S 85W)
2003
Weller
2002
2001
Annual-mean heat flux into ocean 30 W m-2 at
1500 km offshore under persistent low cloud!
How is this net warming at the surface balanced
by ocean heat transports?
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Diurnal Cycle
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Diurnal Cycle
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UPSIDENCE WAVEin ECMWF analysis fields (left)
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VOCALS Regional Experiment (REx)

• VOCALS-Rex will collect datasets required to
  address a set of issues that are organized into
  two broad themes
• Aerosol-cloud-drizzle interactions in the marine
  boundary layer (MBL) and the physicochemical and
  spatiotemporal properties of aerosols
• Chemical and physical couplings between the
  upper ocean, the land, and the atmosphere.

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• AEROSOL-CLOUD-DRIZZLE HYPOTHESES
• Variability in the physicochemical properties of
  aerosols has a measurable impact upon the
  formation of drizzle in stratocumulus clouds over
  the SEP
• Precipitation is a necessary condition for the
  formation and maintenance of pockets of open
  cells (POCs) within stratocumulus clouds
• The small effective radii measured from space
  over the SEP are primarily controlled by
  anthropogenic, rather than natural, aerosol
  production, and entrainment of polluted air from
  the lower free-troposphere is an important source
  of cloud condensation nuclei (CCN)
• Depletion of aerosols by coalescence scavenging
  is necessary for the maintenance of POCs.

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• COUPLED-OCEAN-ATMOSPHERE-LAND HYPOTHESES
• Oceanic mesoscale eddies play a major role in
  the transport of heat and fresh water from
  coastally upwelled water to regions further
  offshore
• By changing the physical and chemical properties
  of the upper ocean, upwelling has a systematic
  and noticeable effect on aerosol precursor gases
  and the aerosol size distribution over the SEP
• The diurnal subsidence wave (upsidence wave)
  originating in northern Chile/southern Peru has
  an impact upon the diurnal cycle of clouds that
  is well-represented in numerical models
• The entrainment of cool fresh intermediate water
  from below
• the surface layer during mixing associated with
  energetic near-inertial oscillations generated by
  transients in the magnitude of the trade winds is
  an important process to maintain heat and salt
  balance of the surface layer of the ocean in the
  SEP.

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VOCALS-REx Platforms
NSF C-130
NOAA Ronald H Brown
DoE ASP G-1
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NSF C-130 Payload

• Standard instruments Microphysics, Turbulence,
  Thermodynamics suite
• Remote sensing Wyoming Cloud Radar
  (zenithnadirslant), Cloud Lidar (zenith),
  Microwave radiometer (183 GHz, zenith), AIMR
  (nadir), MODIS Airborne Simulator (MASTER,
  nadir), BBRs
• Chemistry/aerosols/clouds LDMA, RDMA, ToF Mass
  Spec, nephelometer, PSAP, CN counters
  (ultrafine), CCN, CVI, Cloud water collector,
  Impactors
• Dropsondes

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NOAA Ronald H Brown Payload

• Remote sensing Cloud profiling radar (94 GHz,
  motion stabilized), C-band scanning radar,
  Microwave radiometer (21/32/90 GHz), Laser
  ceilometer, Wind profiler, BBRs
• Meteorology Flux tower, Turbulence, Meteorology
  suite
• Oceanography XBTs, ADCP, SeaSoar, Ocean
  microstructure profiles, SST sensors, thermistor
  chains
• Chemistry/Aerosols DMS fluxes, Aerosol
  composition (impactors, PILS), Ozone, Radon,
  Nephelometers, PSAP, DMA/APS, CCN (5 channels)

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CIRPAS Twin Otter Payload
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DoE G-1 Payload
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• VOCALS
• REx
• Study
• Region

Oct-Nov 2008 NSF C-130 NOAA Ronald H
Brown CIRPAS Twin Otter DoE G-1
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VOCALS-REx Ship sampling strategy

• Ronald H Brown will sample from fixed positions
  at 20S and 75, 80, 85 W
• 2nd ship will perform butterfly patterns (500 km
  on a side) to carry out ocean mesoscale survey

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VOCALS-REx Flight-plan for C-130 Cross-section
missions
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VOCALS-REx Flight-plan for C-130 POC-Drift
missions
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Drizzle, LWC, w, and pressure perturbations in
stratocumulus
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VOCALS Modeling Program (Mod)
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VOCALS aims to develop a Modeling Framework for
Interannual Climate Predictions
CAM NCEP GFDL UCLA
AGCM Atmosphere General Circulation
Model OGCM Ocean General Circulation Model
AGCM
RAM
POP MIT
OGCM
ROMS
ESMF Infrastructure
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VOCALS Legacy

• Improved large scale coupled ocean-atmosphere
  model simulations and predictions of the SEP
  climate system through a coordinated modeling and
  observational program
• Integrated datasets (IDs), and complete data
  archive
• Development of a multi-scale simulation and
  prediction system
• Education and training for both US and regional
  climate scientists.

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What is an integrated dataset (ID) ?

• An integrated dataset distills field measurements
  from multiple platforms and ancillary data
  (reanalyses, satellites) into a compact,
  self-contained form convenient for modelers
  without expert field knowledge.
• Relevant data depends on target modeling
  audience
• GCMs (statistical comparison of global model
  output)
• GCMs or regional models run in forecast mode.
• Single column model (SCM) versions of GCMs.
• Cloud-resolving models (CRMs).
• ARM (esp. Minghua Zhang of Stony Brook) has
  pushed IDs for SCM/CRMs to ensure their data has
  impact.
• It is important that the VOCALS community
  (modelers and observationalists) defines useful
  integrated datasets.

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EPIC2001 Stratocumulus Cruise exploration of SE
Pacific stratus

• Issues Control of cloud fraction, albedo
• Findings
• Extensive evaporating drizzle drives low-albedo
  patches of POCs in aerosol-poor air masses.
• Strong diurnal cycle of cloud thickness amplified
  by Andes-induced subsidence wave

POCs
WHOI stratus buoy
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MODIS 250m visible imagery
In the SEP near the coast Pockets of Open Cells
(POCS) rarely develop, but away from the coast
they are more frequent and extended than in other
Scu regions.
Are these behaviors evidence of strong links
between aerosol and cloud macrophysical
structure? What is the role of drizzle?
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Modeling issues in the SEP I

• In the SEP, coupled atmosphere-ocean models have
  difficulties in simulating stratocumulus clouds
  and produce large SST and surface wind errors,
  and show a double ITCZ bias.
• A realistic simulation of the tropical
  stratocumulus by an AGCM (with prescribed SSTs)
  does not guarantee a single ITCZ in the coupled
  mode.
• A CGCM can produce a weak double ITCZ and yet
  obtain a very symmetric SST distribution in the
  eastern Pacific. The OGCMs, therefore, provide
  their own contribution to a double ITCZ bias.
• The oceanic wind-driven circulation in the SEP
  develops a vigorous mesoscale and submesoscale
  eddy field that covers a much larger area than
  the coastal upwelling zone. The extent to which
  OGCMs capture this extension is unclear.
• Global OGCMs have difficulties with the
  simulation of eddy transports of heat, salinity,
  and nutrients in the SEP, most plausibly because
  they do not resolve well the regional upwelling
  currents and eddies.

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Annual mean precipitation
Annual Mean Precipitation - IPCC Models
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Modeling issues in the SEP II

• The oceanic wind-driven circulation in the SEP
  develops a vigorous mesoscale and submesoscale
  eddy field that covers a much larger area than
  the coastal upwelling zone. The extent to which
  OGCMs capture this extension is unclear.
• Global OGCMs have difficulties with the
  simulation of eddy transports of heat, salinity,
  and nutrients in the SEP, most plausibly because
  they do not resolve well the regional upwelling
  currents and eddies.

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ROMSSimulation
(From J. McWilliams)
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Modeling issues in the SEP III

• Mesoscale atmospheric processes, such as those at
  work for pockets of open cells (POCS), influence
  cloud properties over the SEP. The PBL
  parameterization of AGCMs does not adequately
  consider those processes.
• Microphysical processes affect cloud properties
  in the SEP. The variability of those processes is
  strongly influenced by the dispersal of
  continental aerosols, which can enhance cloud
  optical thickness and influence cloud liquid
  water through suppression of drizzle.
• ContemporaryCGCMs do no address the potentially
  important feedbacks associated with the effects
  of aerosol upon the coupled ocean-atmosphere
  system.

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Error in TOA net SW radiation (W m-2) caused by
assumption of constant cloud droplet effective
radius (here assumed to be 15 microns)
Difference between TOA assuming constant and
satellite-estimated cloud droplet radius
Coastal clouds not reflective enough
Remote clouds too reflective
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VOCALS

• The overall goal of VOCALS is to develop and
  promote scientific activities leading to improved
  understanding, model simulations, and predictions
  of the southeastern Pacific (SEP) coupled
  ocean-atmosphere-land system, on diurnal to
  interannual timescales.
• The focus of VOCALS in the SEP includes
• Interactions with remote climates.
• Systematic biases of atmosphere-ocean GCMs.
  
• Ocean budgets of heat, salinity, and
  nutrients.
• Aerosol-cloud-drizzle interactions in the
  marine PBL.

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MODELING HYPOTHESES

• The CGCMs difficulties in capturing the effects
  on the SEP of an upstream region with strong
  coastal upwelling and high Sc incidence are
  crucial contributors to the model errors in the
  region.
• In the atmosphere, southeast trades from the
  South American coast flow from a cool and dry PBL
  over strong SST gradients and regions where trade
  cumuli form moistening the lower troposphere.
  These processes are not well represented by
  AGCMs.
• In the ocean, mesoscale eddies not captured by
  OGCMs play a major role in the transport of heat
  and fresh water from coastally upwelled water to
  regions further offshore.
• An approach based on regional and high-resolution
  ROAM embedded within the seasonally and
  interannually varying global climate can overcome
  these model difficulties.

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AEROSOL-CLOUD-DRIZZLE HYPOTHESES

• Variability in the physicochemical properties of
  aerosols impacts the formation of drizzle in
  stratocumulus clouds.
• Upwelling, by changing the physical and chemical
  properties of the upper ocean, has a systematic
  and noticeable effect on aerosol precursor gases
  and the aerosol size distribution in the MBL.
• Precipitation is necessary for the formation of
  pockets of open cells (POCs) within stratocumulus
  clouds, and depletion of aerosols by coalescence
  scavenging is necessary for the maintenance of
  POCs.
• Anthropogenic aerosol production is a source of
  cloud condensation nuclei (CCN) and controls the
  effective cloud radius over the SEP.

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VOCALS Program

• VOCALS-Rex
• Airborne Campaign PBL clouds, aerosol
• Ship CampaignPBL clouds, aerosol, ocean eddies

• VOCALS Modeling
• Diagnosis and hypothesis/testing exps
• Simulation and/or prediction for the austral
  spring with CGCMs and ROAMs
• Assessment of the impact of enhanced observations
  by VOCALS-Rex
• Organized modeling activities

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Elements of VOCALS-REX

• SEP has research-grade buoys and strategic
  islands
• Yearly maintenance cruises of the IMET buoy since
  2000 have provided data along 20S. This cruises
  will continue until 2008
• Highly committed regional partners, primarily in
  Chile, Peru and Ecuador
• Possible European presence PRIMO

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Chilean and Peruvian (250K and 70K)
International Components of VOCALS
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MODELING and SATELLITE RETRIEVAL VALIDATION GOALS

• Improved simulation of the large-scale
  circulation in the atmosphere and mesoscale ocean
  eddy transports of heat and biogenic species
  offshore over the SEP
• b) Improved representation of the aerosol
  indirect effects over the SEP by regional and/or
  global models
• c) Detailed validation of techniques that
  provide satellite estimates of Scu microphysical
  properties (e.g. effective radius or cloud
  droplet number concentration from MODIS) and
  precipitation (from CloudSat or MODIS) under
  conditions that can be of broken cloudiness on
  the pixel scale

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EPIC Contributions

• Much was learned on ITCZ variability and the
  cross-equatorial flow in the eastern Pacific.
• A new parameterization of oceanic solar
  absorption based on satellite color and
  chlorophyl concentration was developed by using
  radiative flux profiles from EPIC. This is used
  derive surface fluxes from the TAO buoy network.
• The simulation of PBL height over the eastern
  Pacific by NCAR CCSM2 was evaluated by using EPIC
  data.
• The methodology to obtain ship-based liquid water
  path (LWP) estimates in marine stratus was
  improved and a new probabilistic approach for the
  relationship between cloud LWP and cloud fraction
  (CF) was developed.
• The data motivated a lot of work with cloud
  ensemble, regional and global models.
• Butthe major problems in the southeastern
  Pacific, which in some ways motivated EPIC,
  remain largely unsolved.