Pacific Sub tropical circulation in ORCA025 and ORCA05

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Pacific (Sub) tropical circulation in ORCA025 and
ORCA05

• DRAKKAR Meeting 2007
• Joke Lübbecke

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Introduction SST STCs Zonal
Currents NGCU Conclusions
Schott et al., 2004
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Introduction SST STCs Zonal
Currents NGCU Conclusions

• In ORCA05 some problems in the tropical pacific
• no Tsuchiya Jets
• EUC too deep
• transport too high

better representation with higher resolution?

• Differences between the ORCA025 experiments
• KAB001 (CORE forcing, weak 3-dim restoring in
  high lat.)
• KAB002 (CORE forcing, strong surface restoring)
• G70 (ERA-40, strong surface restoring)

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Introduction SST STCs Zonal
Currents NGCU Conclusions
Nino3 SST
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Introduction SST STCs Zonal
Currents NGCU Conclusions
Meridional Overturning Stream Function
20/15 Sv
ORCA025 KAB001 G70
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Introduction SST STCs Zonal
Currents NGCU Conclusions
STC Strength
explaination for different trends ???
ORCA05 KAB001 G70
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Introduction SST STCs Zonal
Currents NGCU Conclusions
EUC mean equatorial zonal velocity
0.9
0.9
ORCA05
ORCA025
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Introduction SST STCs Zonal
Currents NGCU Conclusions
Mean zonal velocity at 155W
ORCA05
ORCA025
Tsuchiya Jets (NSCC, SSCC) in ORCA025
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Introduction SST STCs Zonal
Currents NGCU Conclusions
Tsuchiya Jets
eastward velocities averaged over 26.0lt s lt27.0
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Introduction SST STCs Zonal
Currents NGCU Conclusions
Mean zonal velocity at 155W
0.80 m/s
0.85 m/s
1991-2000
KAB001
G70
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Introduction SST STCs Zonal
Currents NGCU Conclusions
mean EUC Transport
in density range 22.5ltslt26.0
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Introduction SST STCs Zonal
Currents NGCU Conclusions
EUC Transport variability
annual cycle
KAB001 KAB002 G70
at 155W, in density range 22.5ltslt26.0
KAB001 G70
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Introduction SST STCs Zonal
Currents NGCU Conclusions
Mean velocity in 150m depth
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Introduction SST STCs Zonal
Currents NGCU Conclusions
7S section
0.1
0.35
0.4
ORCA2
ORCA05
ORCA025
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Introduction SST STCs Zonal
Currents NGCU Conclusions
Transport
transport variability

• mean transport
• (24.0 ltslt 26.7)
• 5S to 10S average
• ORCA2
• 13 Sv
• ORCA05
• 20 Sv
• ORCA025
• 20 Sv

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Introduction SST STCs Zonal
Currents NGCU Conclusions

• improvements with ORCA025
• Tsuchiya Jets present
• EUC extension not that deep
• more realistic EUC transport
• representation of western boundary current
• KAB001 compared to G70
• structure of zonal currents and OT similar
• all wind driven features weaker in G70
• EUC transport variability in phase with offset
• open question
• different STC trends ORCA05 gt G70 gt KAB001

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KAB001 KAB002
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ORCA05 (KAB042) ORCA025 (KAB001) ORCA025
(KAB002) ORCA025 (G70)