Pacific Decadal Oscillation :

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PDO is a long-lived El Niño-like pattern of Pacific climate variability.
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Both PDO and ENSO have similar spatial climate fingerprints yet the major difference is that PDO persists for 20-30 years while the typical ENSO persists for 6 to 18 months.
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The PDO, like ENSO, consists of a warm and cool phase which alters upper level atmospheric winds.
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During a “warm”, or “positive”, phase, the west Pacific becomes cooler and part of the eastern ocean warms; during a “cool” or “negative” phase, the opposite pattern occurs.
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Shifts in the PDO phase can intensify or diminish the impacts of ENSO according to its phase.
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If both ENSO and the PDO are in the same phase, it is believed that El Niño/La Nina impacts may be magnified.
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This in turn affects the northeast Indian summer monsoon during its negative phase.
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Conversely, if ENSO and the PDO are out of phase, it has been proposed that they may offset one another, preventing “true” ENSO impacts from occurring.
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