This study found that the spring (February-April) rainfall in northern Taiwan has fluctuated concurrently with the Pacific Decadal Oscillation (PDO) since the early 20th century. It is proposed that this fluctuation in spring rain is induced by the tropical sea surface temperature (SST) anomaly embedded in the PDO, which has been known to oscillate in opposite phase to the SST in the extra-tropical North Pacific. When the PDO index is positive (negative), the SST over the tropical Central-Eastern Pacific is warmer (colder) than normal, and a low-level anti-cyclonic (cyclonic) anomalous flow is induced over the Philippine Sea. This anomalous anti-cyclonic (cyclonic) flow results in southwesterly (northeasterly) anomalous winds to the east of Taiwan and enhances (reduces) the trough extending southwestward from southern Japan to northern Taiwan. As a consequence, more (less) spring rain occurs in northern Taiwan during the positive (negative) PDO phases.
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