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Mechanisms of land rainfall anomalies associated with tropical Atlantic variability Seek mechanisms for SST to land impacts examined by e.g., Hastenrath and Heller 1977, Moura & Shukla, 1981; …Enfield, 1996; … Saravanan & Chang 2000, Paegle & Mo, 2002; here focus on S. Trop. Atlantic impacts on NE Brazil Intermediate atm/land model QTCM simulations; moist static energy diagnostics; intervention experiments, used on other teleconnection pbs. (e.g. Su and Neelin 2002, 2003) Climate Systems Interactions group (CSI) http://www.atmos.ucla.edu/~csi J. David Neelin and Hui Su, U.C.L.A
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NCEP Brazil Precip vs. SST SST regression on Brazil rainfall index (box) NCEP precip (MAM) nino3.4 effects removed 1982-98; K/(mm/day) 90% confidence stippled NCEP precip regression on S. Atl. SST (30S - 5N) MAM nino3.4 effects removed (mm/day)/K 90% confidence stippled See also Paegle & Mo 2002
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SST on Northern Nordeste Brazil Precip TAGA QTCM (MAM) 95% confidence shaded 1950-2000 ensemble of 10 (K/(mm/day)) GOGA QTCM (MAM) nino3.4 effects removed 90% confidence shaded 1950-2000 ensemble of 10 SST regression on Brazil rainfall index (box) See also Saravanan & Chang 2000
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Precip. regression on S. Atl SST (30S-5N) MAM TAGA QTCM (90%) confidence stippled 1982-98 ensemble of 10 GOGA QTCM nino3.4 effects removed (90%) confidence stippled 1982-98 ensemble of 10 (mm/day)/K
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CMAP Precip regression on S. Atl. SST (30S-5N) MAM nino3.4 linear effects removed 90% confidence stippled 1982-98 (mm/day)/K
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NCEP regression on S. Atl. SST (30S-5N) MAM Temperature (1000-200mb avg) nino3.4 effects removed 90% confidence stippled 1982-98 (K/K) Moisture (1000-850 mb avg) nino3.4 effects removed 90% confidence stippled 1982-98 (g/kg)/K
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Obs SST/GOGA T s regression on S. Atl. SST index (30S-5n) MAM nino3.4 linear effects removed 90% confidence stippled 1982-98 (K/K)
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GOGA QTCM regression on S. Atl. SST (30S-5N) Tropospheric temp. (1000-200 mb avg) nino3.4 effects removed 90% confidence stippled (K/K) Moisture (vert. avg) nino3.4 effects removed 90% confidence stippled 1982-98 ensemble of 10 (g/kg)/K
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GOGA (v · q) regression on S. Atl. SST (30S-5N) MAM GOGA (v · q) ´ regression on S. Atl. SST (30S-5N) MAM nino3.4 effects removed 90% confidence stippled 1982-98 ensemble of 10 (W/m 2 )
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TAGA QTCM temperature (1000-200 mb avg) regression on S. Atl. SST (30S-5N) MAM 90% confidence stippled 1982-98 ensemble of 10 (K/K)
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S. Atl. SST (30S-5N) STAGA (MAM98) – Clim Obs SST/QTCM T s (K) QTCM Precip. ensemble of 10 (mm/day)
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STAGA (MAM98) - Clim Temperature (1000-200 mb avg) anom. (K) Moisture (vert. avg) anom. (g/kg)
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STAGA QTCM anomalies (MAM98) - Clim Moisture advection v · q (vert. avg) contour 3 W/m 2 Moisture convergence by divergent wind component M q ·v (vert. avg) contour 20 W/m2
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STAGA Prec – Clim MAM98 Control Precip. anom. (mm/day) Experiment testing importance of advection: (v · q) anomalies suppressed Precip. anom. (mm/day)
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S. Trop. Atl. SST on northeastern Brazil rain: Hypothesized mechanism Warm SST higher moisture over ocean Advection raises moisture over downwind land [little effect where convectively stable] In & near clim. convection zone, (v· q)´, incr. P´ slightly. Main effect: balanced by moist static energy divergence M · v´. Implies low level moisture convergence M q · v´ so P´ =(M q /M + 1) (v· q)´ Mq/M large amplifies effect of (v· q)´
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Paegle and Mo (2002) DJF Precip. (merged Hulme/Xie-Arkin data) Correlation between seasonal mean SSTAs and RPC1,2 for DJF Correlation between SSTAs and RPC2 for SON and MAM
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Saravanan & Chang (2000), [1] Regression Obs SST on Nino-3 (C) Correlation higher in west See also Enfield & Mayer (1997)
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Saravanan & Chang (2000), [2] CCM3 AGCM with obs SST 1950-1994 Squared correlation of SST to Northern Nordeste Brazil precipitation index (box) (11-3S,46-38W) MAM season
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Saravanan & Chang (2000), [3] MAM Precip regression (a) NINO3 (b)NTA SST index (4N-20N, approx 15W-78W)
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