Three Putative Types of El Nino Revealed by Spatial Variability in Impact on Australian Wheat Yield

The El Niño-Southern Oscillation (ENSO) phenomenon significantly impacts rainfall and ensuing crop yields in many parts of the world. In Australia, El Niño events are often associated with severe drought conditions. However, El Niño events differ spatially and temporally in their manifestations and impacts, reducing the relevance of ENSO-based seasonal forecasts. In this analysis we identify three putative types of El Niño among the 24 occurrences since the beginning of the 20 century. The three types are based on coherent spatial patterns (‘footprints’) found in El Niño impact on Australian wheat yield. This bio-indicator reveals aligned spatial patterns in rainfall anomalies, indicating linkage to atmospheric drivers. Analysis of the associated ocean/atmosphere dynamics identifies three types of El Niño differing in timing of onset and location of major ocean temperature and atmospheric pressure anomalies. Potential causal mechanisms associated with these differences in anomaly patterns need to be investigated further using the increasing capabilities of general circulation models. Any improved predictability would be extremely valuable in forecasting effects of individual El Niño events on agricultural systems.