Changes in teleconnection patterns in response to different types of El Niño Southern
Oscillation (ENSO), classified by the positioning of SST anomalies in: East Pacific
(EP) and Central Pacific (CP) and their impacts on SST variability on the Tropical
North Atlantic (TNA) and tropical South American precipitation, during the positive
and negative phases of Atlantic Multidecadal Oscillation (AMO) were evaluated for
the 1901-2010 period, using the composite method for the quarterly anomalies.
These analyses were applied to atmospheric and oceanic anomaly variable fields
(Sea Surface Temperature-SST, precipitation, 200 hPa stream function, 1000 hPa
horizontal winds and mean sea level pressure). Regarding the distribution of ENSO
events, the results shows consistency with previous studies on the relation between
AMO and ENSO, with the ENSO events occurring more frequently during the
negative phase of AMO. The El Niño (La Niña) events, independent of the type (EP
or CP), during the positive (negative) phase of AMO were followed by a warming
(cooling) on TNA after their mature phases. The dynamics of this relationship involve
variations in Walker's circulation or variations in the Pacific North American (PNA)
teleconnection pattern. On the other hand, for the El Niño (La Niña) years that
occurred during the negative (positive) phase of the AMO, no significant variations
were observed in the SST over the TNA. These results shows the important role of
the SST anomaly precondition in the Tropical Atlantic and north, associated to AMO
phases, in defining teleconnection patterns in response to ENSO. When ENSO and
AMO are both in the same phase, the patterns of extratropical teleconnections are
dominant, through the PNA, in addition, they have anomalies with the same sign in
the tropical Pacific and in the TNA. On different phases of ENSO and AMO, the
tropical teleconnection patterns are dominants, through the Walker circulation and
the inter-basin zonal gradient that is intensified due to the observed SST anomalies
in the Pacific Ocean and the neutral pattern in the Atlantic. These circulations pattern
changes affect the rainfall over tropical South America. The results presented here
highlight the importance of low frequency oscillations in defining the teleconnection
patterns between the Pacific and AT oceans, not discussed previously.
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