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Influence of the IOD on the relationship between El Niño Modoki and the East Asian‐western North Pacific summer monsoon
Author(s) -
Feng Juan,
Chen Wen
Publication year - 2014
Publication title -
international journal of climatology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.58
H-Index - 166
eISSN - 1097-0088
pISSN - 0899-8418
DOI - 10.1002/joc.3790
Subject(s) - anticyclone , climatology , indian ocean dipole , anomaly (physics) , walker circulation , east asia , geology , south asia , atmospheric sciences , environmental science , oceanography , el niño southern oscillation , geography , physics , condensed matter physics , history , china , archaeology , ethnology
The relationship between El Niño Modoki and the East Asian‐western North Pacific summer monsoon ( EA‐WNPSM ) has been revealed to be under the influence of Indian Ocean Dipole ( IOD ). When a pure El Niño Modoki occurs without a positive IOD , a strong EA‐WNPSM is observed with a significant anomalous low‐level cyclone over the western North Pacific ( WNP ), excessive rainfall there and deficient Meiyu–Baiu rainfall. In contrast, when an El Niño Modoki happens simultaneously with a positive IOD , the anomalous EA‐WNPSM tends to be much weaker. This difference is attributed to a positive IOD effect. The results demonstrate that a positive IOD usually leads to a strong South Asian summer monsoon heating, which further causes easterly anomalies in the western Pacific. These anomalous easterlies tend to strengthen the WNP anticyclonic vorticity leading to a weak EA‐WNPSM . Therefore, a positive IOD weakens the relationship between the El Niño Modoki and the EA‐WNPSM . In addition, numerical experiments verified that the strong low‐level WNP cyclonic anomaly is built through the off‐equatorial heating associated with the local cyclonic circulation. The anomalous WNP anticyclonic vorticity induced by a positive IOD weakens this off‐equatorial heating, thus leading to a weak EA‐WNPSM .