The relative roles of the South China Sea summer monsoon and ENSO in the Indian Ocean dipole development
The influence of El Niño-Southern Oscillation (ENSO) on the Indian Ocean Dipole (IOD), a coupled ocean–atmosphere mode of interannual climate variability, has been widely investigated over recent decades. However, a latest study indicates that the South China Sea summer monsoon (SCSSM) might also be responsible for IOD formation. Furthermore, an abnormal SCSSM does not always coincide with ENSO during boreal summer (June–August, JJA); consequently, the individual and combined effects of the SCSSM and ENSO on the IOD remain elusive. This study shows that the amplitude of the IOD tends to be much stronger under the coexistence of SCSSM and ENSO than that under individual SCSSM or ENSO events during JJA and autumn. The findings also indicate that the SCSSM and ENSO play the dominant role around the eastern and western poles of the IOD, respectively. An anomalous local Hadley circulation closely related to the stronger SCSSM favors anomalous southeasterly off Sumatra and Java during JJA, which enhance oceanic upwelling and subsequently result in cooling of the sea surface temperature (SST) over this area. Similarly, it can be envisaged that the contemporaneous ENSO could influence JJA SST anomalies over the western Indian Ocean via the Walker circulation coupled with oceanic variations.
KeywordsIndian dipole mode South China Sea summer monsoon El Niño–Southern oscillation Individual and combined effects
This work was jointly supported by the National Natural Science Foundation of China (NSFC) Project (41790474; 41530424) and the SOA International Cooperation Program on Global Change and Air–Sea Interactions (GASI-IPOVAI-03). The ERSST v5 dataset was derived from the International Comprehensive Ocean–Atmosphere Dataset (ICOADS) (https://www.esrl.noaa.gov/psd/data/gridded/data.noaa.ersst.v5.html). NCEP/NCAR and SODA (version 2.2.4) reanalysis datasets were available at http://www.esrl.noaa.gov/psd/data/gridded/ and https://climatedataguide.ucar.edu/climate-data/soda-simple-ocean-data-assimilation, respectively.
- An SI, Jin FF (2004) Nonlinearity and asymmetry of ENSO. J Clim 17:2399–2412. https://doi.org/10.1175/1520-0442(2004)017%3c2399:NAAOE%3e2.0.CO;2 CrossRefGoogle Scholar
- Ashok K, Guan Z, Saji N, Yamagata T (2004) Individual and combined influences of ENSO and the Indian Ocean dipole on the Indian summer monsoon. J Clim 17:3141–3155. https://doi.org/10.1175/1520-0442(2004)017%3c3141:IACIOE%3e2.0.CO;2 CrossRefGoogle Scholar
- Kalnay E, Kanamitsu M, Kistler R, Collins W, Deaven D, Gandin L, Iredell M, Saha S, White G, Woollen J (1996) The NCEP/NCAR 40-year reanalysis project. Bull Am Meteorol Soc 77:437–471. https://doi.org/10.1175/1520-0477(1996)077%3c0437:TNYRP%3e2.0.CO;2 CrossRefGoogle Scholar
- Klein SA, Soden BJ, Lau NC (1999) Remote sea surface temperature variations during ENSO: evidence for a tropical atmospheric bridge. J Clim 12:917–932. https://doi.org/10.1175/1520-0442(1999)012,0917:RSSTVD.2.0.CO;2 CrossRefGoogle Scholar
- Lau NC, Nath MJ (2004) Coupled GCM simulation of atmosphere–ocean variability associated with zonally asymmetric SST changes in the tropical Indian Ocean. J Clim 17:245–265. https://doi.org/10.1175/1520-0442(2004)017%3c0245:CGSOAV%3e2.0.CO;2 CrossRefGoogle Scholar
- Li JP, Wu GX, Hu DX (2011a) Ocean-atmosphere interaction over the joining area of Asia and Indian-Pacific ocean and its impact on the short-term climate variation in China (in Chinese), vol 1. China Meteorological Press, Beijing, p 516Google Scholar
- Li JP, Wu GX, Hu DX (2011b) Ocean–Atmosphere interaction over the joining area of Asia and Indian-Pacific ocean and its impact on the short-term climate variation in China (in Chinese), vol 2. China Meteorological Press, Beijing, p 565Google Scholar
- Liu T, Li J, Li Y, Zhao S, Zheng F, Zheng J, Yao Z (2017) Influence of the May Southern annular mode on the South China Sea summer monsoon. Clim Dyn 51:1–13Google Scholar
- Nan SL, Li JP (2005a) The relationship between the summer precipitation in the Yangtze River valley and the boreal spring Southern Hemisphere annular mode: I Basic facts. Acta Meteorol Sinica 63(6):837–846. https://doi.org/10.3321/j.issn:0577-6619.2005.06.001 (in Chinese with English abstract) CrossRefGoogle Scholar
- Nan SL, Li JP (2005b) The relationship between the summer precipitation in the Yangtze River valley and the boreal spring Southern Hemisphere annular mode: II The role of the Indian Ocean and South China Sea as an “oceanic bridge”. Acta Meteorol Sinica 63(6):847–856. https://doi.org/10.11676/qxxb2005.081 (in Chinese with English abstract) CrossRefGoogle Scholar