Processes and boreal summer impacts of the 2004 El Nino Modoki: An AGCM study

The sea surface temperature anomalies (SSTA) of tropical Pacific in the boreal summer of 2004 show a distinct tripolar pattern with warm SSTA in the central tropical Pacific, flanked on both sides by cold SSTA. The distinct conditions during the boreal summer of 2004 and the following winter were catalogued as a new coupled phenomenon named El Nino Modoki in a recent generalized study. The 2004 event is unique in the sense that it occurred without any co-occurring IOD, thereby without any possibility of external modulation of its processes and impacts in the tropics. Using observed data since 1979, we show that the 2004 event indeed involves the distinct equatorial coupled ocean-atmosphere dynamics different from the conventional El Nino. Further, using an AGCM, we confirm that during boreal summer anomalous twin Walker circulation cells associated with the El Nino Modoki SSTA give rise to observed rainfall anomalies in the tropics. Citation: Ashok, K., S. Iizuka, S. A. Rao, N. H. Saji, and W.- J. Lee (2009), Processes and boreal summer impacts of the 2004 El Nino Modoki: An AGCM study, Geophys. Res. Lett., 36, L04703, doi:10.1029/2008GL036313.