Anomalous winter climate conditions in the Pacific rim during recent El NiA±o Modoki and El NiA±o events

Present work compares impacts of El NiA +/- o Modoki and El NiA +/- o on anomalous climate in the Pacific rim during boreal winters of 1979-2005. El NiA +/- o Modoki (El NiA +/- o) is associated with tripole (dipole) patterns in anomalies of sea-surface temperature, precipitation, and upper-level divergent wind in the tropical Pacific, which are related to multiple boomerangs of ocean-atmosphere conditions in the Pacific. Zonal and meridional extents of those boomerangs reflect their independent influences, which are seen from lower latitudes in the west to higher latitudes in the east. In the central Pacific, more moisture is transported from the tropics to higher latitudes during El NiA +/- o Modoki owing to displacement of the wet boomerang arms more poleward toward east. Discontinuities at outer boomerang arms manifest intense interactions between tropical and subtropical/extratropical systems. The Pacific/North American pattern and related climate anomalies in North America found in earlier studies are modified in very different ways by the two phenomena. The seesaw with the dry north and the wet south in the western USA is more likely to occur during El NiA +/- o Modoki, while much of the western USA is wet during El NiA +/- o. The moisture to the southwestern USA is transported from the northward shifted ITCZ during El NiA +/- o Modoki, while it is carried by the storms traveling along the southerly shifted polar front jet during El NiA +/- o. The East Asian winter monsoon related anticyclone is over the South China Sea during El NiA +/- o Modoki as compared to its position over the Philippine Sea during El NiA +/- o, causing opposite precipitation anomalies in the southern East Asia between the two phenomena.