Impacts of Regional Mixing on Circulations in the Subtropical and Tropical Pacific Ocean
Remote Features Linked to the South Pacific Subtropical High
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Remote Features Linked to the South Pacific Subtropical High
(hereafter called the “SP high”)
Richard GrotjahnAtmospheric Science Program,
Dept. of LAWR, Univ. of California
Davis, CA 95616, USA
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Our Prior Work on the SP high
• Working hypothesis that there are remote connections to the subtropical high
• Some connections will be visible through the divergent circulation.
• 3 sources of remote forcing.
• (1) Hadley and Walker circulations,
• (2) Rossby wave forcing from East,
• (3) frontal cyclones
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Composites of DJF Monthly Anomaly Data:
• Months of stronger highs minus months of weaker highs show:
• lower SLP to East (purple)• More P (green) West or
westward shift of SPCZ• Dipole (P) & (OLR) S and
SW of high: shift to S.• More P North of ICZ East
Pacific or Northward shift• Enhanced P North of
South America
• Green: significant above (1%)
• Purple: significant below (1%)
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1-pt correlations of Monthly Anomaly Data:
• P shown, OLR similar.
• correlation points respond to events on the same side as the correlation point.
• NW side to ICZ SPCZ
• NE to ICZ & SA
• S & SW sides to midlatitudes
• Blue: significant above (1%)
• Orange: significant below (1%)
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Recent Work: daily mean data
• Data Source:
• NOAA/CDC (Boulder CO, USA)
• NCEP/NCAR reanalysis data
• SLP, U, V
• Ud, Vd, Velocity Potential (VP) from NCL commands.
• Data record:
• 90-day DJF periods shown (122 day NDJF similar)
• Drawn from 01/1990 through 08/2002
• Goal:
• Prior work showed remote links now wish to establish cause and effect.
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Cross-correlation points for SLP & VP
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SLP lagged autocorrelationslag (L) and lead (R) SLP @ pt-8
correlations (CW: 4, 2, 0, -2, -4d)
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Velocity Potential (“VP”)lag (L) and lead (R) SLP @ pt-8
correlations (CW: 8, 6, 4, 2, 0, -2, -4,-6 d)
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Vd - Meridional Divergent Windlag (L) and lead (R) SLP @ pt-11 correlations (CW: 4, 2, 0, -2, -4d)
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VP cross-correlations for SLP on NE side
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DWS cross-correlations for SLP max
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DWS cross-correlations for SLP South side
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Tentative Conclusions• Equatorial and NE side of SP high highly correlated with
pressure in equatorial & E Pacific. Stronger SLP on N side of SP high is followed by lower SLP over SE Asia.
• Stronger SP highs are those SW of the mean position & reinforced by divergent winds from midlatitude cyclones.
• Weaker E Indonesian convection is followed in a few days by expansion of Amazonian velocity potential (VP) min. and westward shift of the SE Pacific VP maximum.
• This last item leads a westward migration of higher than normal SLP on equatorial side of SP high.
• For many points cross spectrum has strong frequency ~40d. (Presumably MJO-like signal, not shown)
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Divergent Wind ComponentsVd Ud
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Velocity Potential (left) & Divergent Wind Speed (right)
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SLP lagged autocorrelationslag (L) and lead (R) SLP @ pt-11 correlations (CW: 4, 2, 0, -2, -4d)
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Vd - Meridional Divergent Windlag (L) and lead (R) SLP @ pt-8
correlations (CW: 4, 2, 0, -2, -4d)