Sea surface temperature associations with the late Indian summer monsoon
- 579 Downloads
Recent gridded and historical data are used in order to assess the relationships between interannual variability of the Indian summer monsoon (ISM) and sea surface temperature (SST) anomaly patterns over the Indian and Pacific oceans. Interannual variability of ISM rainfall and dynamical indices for the traditional summer monsoon season (June–September) are strongly influenced by rainfall and circulation anomalies observed during August and September, or the late Indian summer monsoon (LISM). Anomalous monsoons are linked to well-defined LISM rainfall and large-scale circulation anomalies. The east-west Walker and local Hadley circulations fluctuate during the LISM of anomalous ISM years. LISM circulation is weakened and shifted eastward during weak ISM years. Therefore, we focus on the predictability of the LISM.
Strong (weak) (L)ISMs are preceded by significant positive (negative) SST anomalies in the southeastern subtropical Indian Ocean, off Australia, during boreal winter. These SST anomalies are mainly linked to south Indian Ocean dipole events, studied by Besera and Yamagata (2001) and to the El Niño-Southern Oscillation (ENSO) phenomenon. These SST anomalies are highly persistent and affect the northwestward translation of the Mascarene High from austral to boreal summer. The southeastward (northwestward) shift of this subtropical high associated with cold (warm) SST anomalies off Australia causes a weakening (strengthening) of the whole monsoon circulation through a modulation of the local Hadley cell during the LISM. Furthermore, it is suggested that the Mascarene High interacts with the underlying SST anomalies through a positive dynamical feedback mechanism, maintaining its anomalous position during the LISM. Our results also explain why a strong ISM is preceded by a transition in boreal spring from an El Niño to a La Niña state in the Pacific and vice versa. An El Niño event and the associated warm SST anomalies over the southeastern Indian Ocean during boreal winter may play a key role in the development of a strong ISM by strengthening the local Hadley circulation during the LISM. On the other hand, a developing La Niña event in boreal spring and summer may also enhance the east–west Walker circulation and the monsoon as demonstrated in many previous studies.
KeywordsIndian Summer Monsoon Indian Summer Monsoon Rainfall Southern Indian Ocean Indian Summer Monsoon Onset Western North Pacific Summer Monsoon
Thanks to A. Fischer and G. Reverdin for helpful comments and suggestions during the course of this research. Sebastien Masson provided graphical software for plotting the results. The comments of the editor (J.-C. Duplessy) and three anonymous reviewers are greatly appreciated.
- Ailikun B, Yasunari T (2001) ENSO and Asian summer monsoon: persistence and transitivity in the seasonal march. J Meteorol Soc Japan 79: 145–159Google Scholar
- Besera SK, Yamagata T (2001) Subtropical SST dipole events in the southern Indian Ocean. Geophys Res Lett 28: 327–330Google Scholar
- Chandrasekar A, Kitoh A (1998) Impact of localized sea surface temperature anomalies over the equatorial Indian Ocean on the Indian summer monsoon. J Meteorol Soc Japan 76: 841–853Google Scholar
- Charney JG, Shukla J (1981) Predictability of monsoon. In: Lighthill J, Pierce RP (eds) Monsoon dynamics. Cambridge University Press, Cambridge, UK, pp 99–108Google Scholar
- Hastenrath S, Greischar L (1993) The monsoonal heat budget of the hydrosphere–atmosphere system in the Indian Ocean sector. J Geophys Res 98: 6869–6881Google Scholar
- Lebart L, Morineau A, Piron M (1995) Statistique exploratoire multidimensionnelle. Dunod, pp 439Google Scholar
- Morrison DF (1990) Multivariate statistical methods. 3rd edn, MacGraw Hill, New YorkGoogle Scholar
- Nicholls N (1984) The Southern Oscillation and Indonesian sea surface temperature. Mon Weather Rev 112 424–432Google Scholar
- Nitta T, Yamada S (1989) Recent warming of tropical sea surface temperature and its relationship to the northern hemisphere circulation. J Meteorol Soc Japan 67: 375–383Google Scholar
- Noreen EW (1989) Computer-intensive methods for testing hypotheses: an introduction. John Wiley & Sons, New YorkGoogle Scholar
- Normand C (1953) Monsoon seasonal forecasting. Q J R Meteorol Soc 79: 463–473Google Scholar
- Palmer TN (1994) Chaos and the predictability in forecasting the monsoons. Proc Indian Natn Sci Acad Part A 60: 57–66Google Scholar
- Parthasarathy B, Munot AA, Kothawale DR (1995) All India monthly and seasonal rainfall series: 1871–1993. Theor Appl Climatol 49: 217–224Google Scholar
- Shukla J (1987) Interannual variability of monsoons. In: Fein JS, Stephens PL (eds) Monsoons. Wiley, Chichester, pp 399–464Google Scholar
- Terray P (1994) An evaluation of climatological data in the Indian Ocean area. J Meteorol Soc Japan 72: 359–386Google Scholar
- Webster PJ, Yang S (1992) Monsoon and ENSO: selectively interactive systems. Q J R Meteorol Soc 118: 877–926Google Scholar
- Webster PJ, Magana VO, Palmer TN, Shukla J, Tomas RA, Yanai M, Yasunari T (1998) Monsoons: processes, predictability and the prospects for prediction. J Geophys Res 103(C7): 14,451–14,510Google Scholar
- Webster PJ, Moore AM, Loschnigg JP, Leben RR (1999) Coupled ocean–atmosphere dynamics in the Indian Ocean during 1997–98. Nature 401: 356–360Google Scholar