CLIVAR Pacific panel

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CLIVAR Pacific panel
Report to OOPC-12, IOC/UNESCO, 2-5 May 2007
prepared by Axel Timmermann, presented/edited by
Toshio Suga
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Science questions of Pacific Panel

• Identified at the Panel meeting, Feb 2006
• Why do CGCMs do a poor job in simulating cold
  tongue?
• Why do CGCMs do a poor job in simulating
  southeast Pacific climate
• What is the role of eastward-propagating WWB-SST
  interactions for ENSO?
• What determines the variations of ENSOs?
• How does the interaction between annual cycle and
  ENSOs work?
• What is the origin of Pacific multidecadal
  variability?
• What is the predictability of decadal variability
  in the Pacific?
• Vulnerabilities of present observing systems?
• What new observations are needed?
• How to observe and monitor LLWBCs, assess their
  climate relevance?

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Contents

• Major science questions of Pacific Panel and
  observational requirements
• ENSO Sensitivity to climate change
• ENSO-WWB interactions
• Understanding of SPCZ
• Improving model biases in the eastern tropical
  Pacific
• Interbasin connections on interannual to
  multidecadal timescales
• ENSO metrics
• SPICE
• South Pacific Observing network
• Workshop on Western Tropical Pacific Hatchery
  for ENSO and Global Teleconnections (China, Nov
  2007)

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ENSO sensitivity to climate change

• Background state MJO ? ENSO
• Background state annual cycle ? ENSO
• Background state ? ENSO
• Orbital and millennial timescales meridional
  control of ENSO
• Greenhouse warming meridional, zonal,
  subsurface control of ENSO and annual cycle
• Decadal timescales subsurface and meridional
  control of ENSO (footprinting)

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ENSO sensitivity to climate change Observational
requirements

• Monitoring of SST, thermocline depth, boundary
  and interior transports
• Monitoring of Walker circulation (see Vecchi and
  Soden, Nature 2006)
• Monitoring of ENSO-MJO relationship
• Monitoring of subsurface anomalies (Argo, TAO,
  altimeter)
• Monitoring of heat flux convergences via drifter
  data, Argo data

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ENSO-WWB interactions

• WWB activity modulates and is modulated by ENSO
  (Eisenman, Jin, Lengaigne)
• WWB is modulated by the annual cycle (Hendon and
  Zhang)
• Nature and Dynamics of these interactions still
  unclear
• Evidence for intensification of WWB and WWB-ENSO
  interactions (Jin et al. 2007)
• What background conditions make this interaction
  favorable?

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• East-ward propagating coupled instabilities

ENSO-WWB interactions
WWB modulation by temperature
Eisenman et al. 2005
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ENSO-WWB interactions observational requirements

• Monitoring of zonal temperature advection
• Monitoring of MJO and warm pool heat budget
• Precise knowledge of WWB initial conditions
  (Lengaigne shows large loss of seasonal
  predictability if initial conditions are not well
  determined) Pacific island data, PI-GCOS
• Monitoring of MJO-warm pool front propagation
  (satellites) and subsurface response (TAO,
  altimetry)

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Understanding the South Pacific Convergence Zone

• Why is there a SPCZ?
• How is it connected to the ITCZ?
• How does the SPCZ interact with the MJO?
• How does the SPCZ interact with the SST
• How does the SPCZ respond to tropical and
  extratropical SST forcing on interannual to
  decadal timescales?
• What influence does the SPCZ wind convergence and
  its modulation have on southwest Pacific boundary
  currents?

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Understanding the SPCZ

• Clouds and temperatures in observations (left)
  and NCAR CCSM3 model

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Understanding the SPCZ
Figure 1 Schematic of hypothesised mechanism for
the development of convection along the SPCZ
during an MJO. Convection over Indonesia (1)
associated with the passage of a MJO leads to an
upper tropospheric anticylone (2). Poleward of
the anticyclone, there is a large PV gradient,
associated with the subtropical jet and the
tropopause (3). Equatorward advection of high''
PV air on the eastern flank of the anticylone
leads to an upper tropospheric trough (4), which
induces deep ascent to the east (5). This region
of deep ascent, to the southeast of Indonesia, is
over the SPCZ, an area susceptible to deep
convection. Hence strongly enhanced convection
can be triggered by the deep ascent and
convection develops from Indonesia into the SPCZ
(6).
Matthews et al 2000 QJR
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Understanding the SPCZ observational requirements

• Series of detailed process studies needed (a la
  TOGA-COARE) focusing on cloud formation, boundary
  layer dynamics, atmosphere-ocean interactions
• Relationship between SST, SPCZ, Rain and Salinity
  using satellite data (Aquarius, SMOS)
• Response of ocean to variations in SPCZ (Argo,
  drifter data)
• SPCZ and subduction and mode-water formation
  (Argo, Repeat hydrography)

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Improving model biases in the eastern tropical
Pacific, cold bias and warm bias, SPCZ bias

• Possible origin of cold bias in coupled models
  (missing ocean biology, under-representation of
  TIWs, mixing, missing diurnal cycle of
  insolation, under-representation of Galapagos
  effect, uncertainties in convective
  parameterizations)
• Possible origin of warm bias in stratus regions
  (problems with cloud parameterizations and
  cloud-aerosol interactions, missing Tsuchiya
  jets, lack of horizontal resolution,
  under-representation of eddies in AR4 CGCMs)

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Improving model biases in the eastern tropical
Pacific, cold bias and warm bias

• Clouds and temperatures in observations (left)
  and NCAR CCSM3 model

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Improving model biases in the eastern tropical
Pacific, cold bias and warm and SPCZ bias
observations needed

• Vertical chlorophyll profiles bio-optical
  feedbacks
• Better estimates of eddy-induced heat transports
  in the southeastern Pacific (VOCALS)
• Better observations of Tsuchiya Jets and their
  variability
• Observational estimates of TIW heat budgets
• Focused process study on SPCZ needed!

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Interbasin connections on interannual to
multidecadal timescales
AMO
A weakened MOC leads to a reduction Of the
meridional asymmetry in the eastern Tropical
Pacific, hence a weakening of The annual cycle
and an intensification of ENSO Whether the AMO
reflects variations of the AMOC is still unclear,
although modeling Results suggest a strong
influence of the AMOC on Atlantic SST Challenge
for ocean data assimilation to Establish a
closer link between observed AMO and AMOC
variability AMO Atlantic Multidecadal
Oscillation AMOC Atlantic Meridional
Overturning Circulation ACY
Annual cycle
ENSO
ACY
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Interbasin connections on interannual to
multidecadal timescales, observational
requirements

• Establish better statistical evidence for
  interbasin linkages using paleo-reconstructions
  of AMO (speleothems, drought indices), ENSO and
  annual cycle strength (corals, speleothems,
  varved lake sediments)
• Monitoring of MOC and AMO and their linkages with
  ENSO on decadal and longer timescales
• Monitoring of cross-central America moisture
  transport, stability of AMOC

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ENSO metrics

• Societal relevance, application indices
• Standard Nino X indeces
• Rainfall over Peru and Ecuador, northern
  Australia
• Wave heights along Californian Coast
• Subsurface temperature around Galapagos
• Number of tropical cyclones in western tropical
  Pacific
• Chlorophyll concentration in Nino 3, and Nino 1
  regions
• Upwelling indices in eastern equatorial Pacific,
  along the South and North American coast
• Seasonal forecasts not only of SST but also of
  primary productivity in Nino X regions
  (desirable, but not yet available)
• Coral bleaching indices from NOAAs Reef watch

• Scientific relevance, advancing our
  understanding and prediction
• Standard Nino X indeces
• Standard warm water indices (PMEL web-site)
• MJO variance index (BMRC web-site)
• Second and third order statistics (including
  spectra)
• BJ index
• Transport indices (boundary and interior
  transports)
• SST-lead-lag correlation between east and west
  SSTA
• Growth rate and variance of ENSO as a function of
  calendar month
• Composite of annual cycle strength for El Nino
  and La Nina years
• TIW variance and heat transport
• Individual heat budget terms
• Moisture transport Atlantic-Pacific in
  atmosphere, interannual variations

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Southwest PacIfic Ocean Circulation and Climate
Experiment
Goal Observe, Model, and understand the role of
the SW Pac Ocean in the -Large scale decadal
climate modulation-ENSO -Tasman Sea
area -Generation of local climate signatures
A. Ganachaud, W. Kessler, S. Wijffels, K.
Ridgway, W. Cai, N. Holbrook, M. Bowen, P.
Sutton, B. Qiu, A. Timmermann, D. Roemmich, J.
Sprintall, S. Cravatte, L. Gourdeau, T. Aung
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The Southwest Pacific Ocean
SPCZ
SPCZ
A
A
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Thermocline water currents
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SPICE Field Experiment Overview
Outset for a large scale field experiment
3-North Coral Sea Pilot study
A-Existing large scale programsB-Pilot
studiesC-Sustained observations
1-Monitoring inflow and bifurcation
2-EAC variability monitoring
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SPICE issues on sustainable observations

• Argo floats are not numerous in the region
  because of the risk of getting stranded with
  strong Trade winds pushing the floats while they
  are transmitting their data at the surface.
  expecting some Iridium floats
• Sattelite altimetry is being used, with some
  adaptation to improve the resolution near the
  coast/around islands.
• There are a few stations of surface ocean
  temperature monitoring (e.g. Noumea,
  Chersterfield, Wallis) that could be enhanced.
• HR XBT are a major repeat database, with the
  Tasman Box. We have in mind the possibility of
  improving the Noumea-Solomon Islands line for
  SPICE purposes (presently low resolution).
• Deployment of gliders 3/4 times/year to monitor
  the flow into the Solomon Sea from the South has
  been proposed. This would provide monitoring for
  4 years.
• Deployment of moorings in the Solomon Straits is
  being proposed. This will be a 1-2 year
  monitoring, and we might consider continuous
  measurements in the future because those straits
  are the chokepoint of the southern EUC sources.

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SPICEwww.ird.nc/UR65/SPICE

• Implementation plan in progressBased on existing
  infrastructures and research groupsNeed for a
  process study in the SPCZ

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South Pacific observing network
High density XBT coverage - blue lines Low
density XBT coverage - red lines and green region
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South Pacific observing network
GCOS Surface Network (GSN)
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South Pacific observing network NEEDS

• Integrated data products for South Pacific needed
• Monitoring of South Pacific ocean currents and
  heat and salinity transports needed
• Monitoring of surfaces heat, momentum and
  freshwater fluxes needed
• Monitoring of boundary currents, heat transports
  and extratropical-tropical linkages SPICE

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Workshop on Western Tropical Pacific Hatchery
for ENSO and Global Teleconnections

• Guangzhou CHINA, 26-28 November 2007
• Objectives
• To address key science questions, such as
• does the South China Sea play an important role
  in the climate system or is it merely responding
  to Pacific/Indian forcing
• How important is the South China Sea Throughflow
  in draining heat out of the Pacific?
• What triggered the 2006/07 El Nino event?
• What were the global impacts of the 2006/2007 El
  Nino?
• How good was the forecast skill of the 2006/2007
  El Nino?
• How does the longterm Indian ocean warming affect
  the global climate system (including ENSO)?
• What is the origin of the longterm Indian ocean
  warming?
• How does the warm pool respond to anthropogenic
  climate change (atmospheric versus oceanic
  feedbacks)?
• To further engage the Chinese oceanographic and
  climate research community in CLIVAR
• To link the Chinese observational activities to
  other international field programs
• To seek international coordination in terms of
  field experiment timing and infrastructure
  (sharing ships, common XBT lines, ...), large
  scale modeling projects, ocean, atmosphere and
  coupled.