- Title
- Indian Ocean dipole [in "State of the Climate in 2019"]
- Creator
- Magee, A.; Chen, L.; Luo, J-J.
- Relation
- Bulletin of the American Meteorological Society Vol. 101, Issue 8, p. S229-S232
- Publisher Link
- http://dx.doi.org/10.1175/BAMS-D-20-0077.1
- Publisher
- American Meteorological Society
- Resource Type
- journal article
- Date
- 2020
- Description
- The Indian Ocean dipole (IOD) is an inherent air–sea coupling mode in the tropical Indian Ocean. It originates from local air–sea interaction in the Indian Ocean and/or the forcing associated with the El Niño–Southern Oscillation (ENSO) in the tropical Pacific (Saji et al. 1999; Luo et al. 2010). Typically, IOD events develop in boreal summer, peak in boreal autumn, and terminate rapidly in early boreal winter. During the late boreal spring to autumn 2019, a positive IOD (pIOD) with extreme intensity occurred for the first time since 1997. Prior to the pIOD event in 1997, the previous extreme pIOD event occurred in 1994 (Luo et al. 2007, 2008). In the tropical Pacific, a weak El Niño occurred in the boreal winter of 2018/19 and returned to neutral conditions by the boreal summer of 2019, but the sea surface anomalously warmed there during the autumn of 2019 (Fig. 4.38c). In the tropical Indian Ocean, a weak pIOD occurred during the autumn of 2018 but rapidly deteriorated early in the winter of 2018/19 (Figs. 4.38a,b; Chen and Luo 2019). For the first four months of 2019 (Figs. 4.38 a,b), IOD-related sea surface temperature (SST) anomalies were near zero. Meanwhile, weak surface easterly wind anomalies prevailed over the central equatorial Indian Ocean during the boreal winter of 2018/19 (partly due to the remote influence of the weak El Niño). These anomalies weakened to near zero in March–April 2019 (Fig. 4.38b). Both pIOD- related SST anomalies (SSTA) and easterly wind anomalies started to grow sharply beginning in May 2019 (Fig. 4.38b). The initial SSTA in the southeastern Indian Ocean exhibited cooling along the south coast of Java in May 2019, and then the cooling signal gradually strengthened and expanded toward the west coast of Sumatra and eastern equatorial Indian Ocean (Figs. 4.39b–d). The positive SSTA in the western equatorial Indian Ocean can be traced back to the persistent warming SSTA associated with the Indian Ocean basin mode throughout the late 2018/19 boreal winter and early 2019 spring (Figs. 4.39a,b). Then the anomalously warm SSTA in the western Indian Ocean maintained its intensity throughout June−October 2019 (Figs. 4.38a, 4.39c,d). The negative SSTA in the eastern pole started to grow from May and continued to increase quickly until October (Figs. 4.38a, 4.39b–d).
- Subject
- summer; boreal autumn; el nino; weather
- Identifier
- http://hdl.handle.net/1959.13/1441910
- Identifier
- uon:41575
- Identifier
- ISSN:0003-0007
- Language
- eng
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