SCSIOs recent progress in understanding of the SCS circulation and climate

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SCSIOs recent progress in understanding of the
SCS circulation and climate
Workshop on Western Tropical Pacific Hatchery of
ENSO and Global Teleconnections, Nov. 26-28,
2007, Guangzhou, China

• Dongxiao WANG
• South China Sea Institute of Oceanology, Chinese
  Academy of Sciences, Guangzhou 510301, China

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South China Sea Convergence zone of multi-flow
NW Pac Monsoon
EA Monsoon
SA Monsoon
A. Monsoon
Ding, 2006
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Outline

• Interannual issue
• Seasonal issue
• Intraseasonal/diurnal issue
• Summary

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Interannual
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Vertical structure at the meridional section of
115-120E
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Double-peak in SST of the SCS
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Trade-wind drived variability of the South China
Sea throughflow
Path ABCD used in the Island Rule calculation
and the composite wind stress anomalies during
abnormal events
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Upper 400m heat storage, HC400
Unit J
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Correlation (LST Upper400m HC400)PositiveHC400
lead LST
A1111.25E-120.25E 10.25N-20.25N
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-2
0
-4
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LST increase HC decrease
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Seasonal
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Yongsheng Zhang, 2005
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AIRS Atmospheric Infrared Sounder Data
AIRS is a facility instrument aboard in EOS Aqua
platform. AIRS constitutes an innovative
atmospheric sounding group of visible, infrared,
and microwave sensors.

• AIRS Level 3 Standard Product
• 12 levels water vapor mass mixing ratio
  profile (specific humidity) from 1000 to 100mb
• 24 levels of Atmospheric temperature profile
  from 1000 t0 1.0mb
• Skin temperature and surface air temperature
• Twice daily, 1?x1? longitude/latitude

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Yongsheng Zhang, 2005
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Regional processes hypothesis for the air-sea
interactions during SCS summer monsoon onset
Radiation
Atmosphere
NE
SW
Wet
Dry
Cooling
Warming
EQ.
20ºN
Ocean
wind-evaporation feedback
Down/upwelling
Yongsheng Zhang, 2005
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• 2??????

Seasonal stationary eddies in the western SCS in
spring
Sea surface height monthly, climatology over
1993-2006 from Topex/Poseidon and
Jason-1 Jan.-Jun.
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Location of warm eddies based on Mar-Apr-May
averaged SSHA during 1993-2006
Annual occurrence of warm eddies
SLAgt8cm for most years, except SLAgt5cm in 1994,
1996
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Eddy structure in climatologic hydrographic data
Vertical plots over 111ºE T (upper) S (lower)
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Cruises in 1998 SCSMEX-IOP evolution of eddies
Cruise in April
Cruise in June
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Eddies in the vertical T/S structure, SCSMEX-IOP
Cruise in April, 1998
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Cruise in June 1998 T/S, plus SB ADCP measurement
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Implication of the warm eddies

• yearly view of wind-SSHA coherent patterns,

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SSHA high corresponds to the shear in wind
directions
Possible mechanism for eddy generation
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Effect on the rainfall
Data area (110-120ºE,10-18ºN)
TRMM PR data over March and April during
1998-2005, convective precipitation
SSHAlt0
SSHAgt0
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Intraseasonal/Diurnal
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Intraseasonal varia(a)Altimetry SLA (b)
OFES_Quikscat, cm
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Annualsemi-annual-mode removed, 1998-2003
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SST vs. meridional wind, corr. coeff. 0.51 Red
curve for SST, green curve for wind
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Forced Rossby waves in the western SCS
Longitude-time plot for May 2004 to Sep 2005. (a)
1090-day band-passed QuikScat wind-stress curl.
The variable is averaged over 12ºN-13.5ºN. (b)
Time-longitude plots of intra-seasonal anomalies
of TOPEX/Poseidon SSHA.
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SCS2 pre-onset(ten days prior to 1998/5/16)
SCS2 post-onset(ten days after 5/17)
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Multi-day averaged diurnal cycle and its
variance for SSTs in the three ATLAS buoys
Pre-onset, blue curve Post-onset, red curve
1998 case
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Summary

• Interannual variability in the SCS can be
  explained by local wind and trade wind forcing,
  in term of thermocline adjustment and SCSTF.
• Seasonal cycle of SSHA in the SCS features a warm
  eddy in the west, spring, with influence on the
  regional rainfall.
• SSH-ISV in the western SCS shows wind-driving and
  can be well reproduced by a daily wind-forced
  model.
• Diurnal SST responds to the monsoon onset.

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Acknowledgement

• NSFC, MOST, CAS, CMA Guangzhou Inst.

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THANKS
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