A positive IOD abruptly developed in July-August 2012 bringing much relief to the very dry conditions over India and increasing the possibilities of floods over East Africa during the short rains season there. The positive IOD in the Indian Ocean as identified from the colder SST anomalies off Java-Sumatra coasts (Fig. 1) returned to the Indian Ocean after a three-year gap. Its immediate predecessors were three consecutive positive IODs that have evolved during 2006-2008, the most unusual situations that ever happened in the historical records of the IOD evolutions. Associated with the development of positive 2012 IOD, the Indonesian region suffered from dry conditions and the moisture diverging from the eastern Indian Ocean has converged to northwest Pacific giving rise to above normal rainfall over Philippines region (Fig. 2). That in turn has caused subsidence and warm conditions over Japan in later half of the 2012 summer.
Fig. 1 Global SST anomalies for July-September season.
Fig. 2 Global OLR anomalies for July-September season. Negative OLR anomalies are associated with above normal rainfall.
2012/10/09