ENSO Modoki impact on the Southern Hemisphere storm track activity during extended austral winter

Abstract

Impacts of the recently discovered ENSO Modoki phenomena on extended winter storm track activity in the Southern Hemisphere are examined using the observed rainfall, sea surface temperature, and reanalyzed upper air circulation data for the period 1979-2004. The partial correlation technique is utilized to distinguish the impact of ENSO Modoki events from those of the ENSO and Indian Ocean Dipole (IOD). El Niño Modoki events introduce an anomalous blocking over central eastern Australia, which suppresses the storm track activity from southwest till centraleast, reducing the storm-associated rainfall in southeastern tip and portions of the southeast. On the other hand, the storm track activity in central Argentina is enhanced owing to the strengthened upper air westerlies in this region. The impacts from the ENSO Modoki events are apparently stronger than the individual impacts from the ENSO and IOD events. Copyright 2009 by the American Geophysical Union.