On the relationship of ENSO with rainfall over different parts of Australia

Each year of the 120-year period 1871-1990 has been characterised as having an El Niño (EN) and/or a Southern Oscillation Index minimum (SO) and/or warm (W) or cold (C) water anomalies in equatorial eastern Pacific sea-surface temperatures. Unambiguous ENSO events, defined as those where El Niño existed and both SO and W occurred in the May to August period, showed a very good association with wide-spread droughts in Australia. Ambiguous ENSOW events, defined as those where El Niño existed but SO and W were outside the May to August period, were sometimes associated with widespread droughts or floods, but were mostly associated with droughts in some parts and floods in others. A similar conclusion applied to other events involving one or more of EN, SO and W, and also to non-events (none of EN, SO, W or C). Cold (C) events were mostly associated with widespread floods, but a few were associated with droughts.