Southern Hemisphere Pacific Variability in SODA POP

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Southern Hemisphere Pacific Variability in SODA
POP
Benjamin Giese Yangxing Zheng / TAMU Jim Carton
/ UMD
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SODA
Simple Ocean Data Assimilation

• Optimum Interpolation
• Updating equations
• Analysis Forecast -
• L(Obs - H( Model forecast - Bias
  forecast ))
• Time increment
• 10dy IUA a digital filter
• Data
• Hydrography (MBTs, XBTs, CTDs, floats, Moored
  thermistor chains)
• Satellite data (SST, Altimetry)
• SODA A Reanalysis of Ocean Climate, Carton and
  Giese, 2005 JGR

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POP

• Numerics
• Parallel Ocean Program
• Domain
• global
• Resolution
• 0.4 X 0.25 degree horizontal
• 40 levels (10m near surface)
• Forcing
• ERA-40 daily wind stress
• GPCP precipitation
• Bulk formulae for heat fluxes

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The SODA-POP 1.4.X Series
SODA POP 1.4.0 1958 - 2001 Simulation (no
updating) SODA POP 1.4.2 1958 - 2001
Assimilation SODA POP 1.4.3 2000 - 2004
QuikSCAT Winds SODA POP 1.4.4 1992 - 2001 As
in 1.4.2 with Altimetry
What is different from earlier SODA POP ?

• Regridding algorithms
• XBT droprate
• Vertical correlations
• loosened T-S relation
• SST correlation scale reduced

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SODA-POP 1.4.X
What is available

• For 1958-2004 on a .5 X .5 grid
• Monthly means to 5300m (T, S, u, v, slh, taux,
  tauy)
• 5 day averages at the surface
• 5 day averages from 5S to 5N (T, S, u, v)

Available at http//apdrc.soest.hawaii.edu
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XBT coverage in 1998
http//www.ifremer.fr/sismer/program/gsdc/mc98.gif
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Global hydrographic observations vs depth
Altimetry
Salinity
Temperature
16,000
70,000
Depth
Depth
Change in data coverage
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Growth of ARGO
ARGO float
Sampling profile
S. Wilson, personal communication
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Meridional Thermocline Transport (sv) from
McPhaden Zhang (2002)
9N Neg. Trans
9S Pos. Trans
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SODA 1.4.2 (solid) 1.4.3 (dashed) Transport
(sv) Calculated as in McPhaden Zhang
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Total flow (not just geostrophic) at 9S Green -
Interior Blue - WBC Red - Total
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Bracher Giese GRL, 2001 Temperature
anomaly on the 1025 isopycnal surface
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Linear regression of Zonal Wind Stress - Positive
values show strengthening, negative values show
weakening
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Mean Heat Transport in Petawatts
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Conclusions

• Soda Pop 1.4.X is available ( via ADPRC LAS and
  DODS )
• Decadal Variability of the tropical Pacific
  Circulation
• General Agreement with McPhaden and Zhang
• Stronger Southern Hemisphere response
• Western Boundary processes important
• A change in heat transport after 1976

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Future Work

• Improve Altimetry assimilation(and possibly other
  satellite observations)
• Ocean Tracers (cfcs, tritium, helium etc)