Multi-annual dry episodes in Australian climatic variability

The output from I 10000-year with with the CSIRO Mark 2 coupled global climatic model has been analysed to Investigate the occurrence of multi-year dry episodes for three selected regions of Australia, specifically, the northeast, southeast and Southwest of the continent Results are presented for dry episodes lasting for 8 or more years An episode is defined as I time Interval having consecutive negative rainfall anomalies. but not necessarily a major drought, tor each year of the episode The hydrological consequences of such an episode can persist tor over it century Typically about 30 episodes are found over the 10 000 years of the simulation for each of the three regions. There is little synchronicity between the regions In the Occurrence of the dry episodes. While there is an El Nino/Sothern Oscillation (ENSO) influence associated with these episodes, it is not continuous over the duration of an episode Composites of sea surface temperature anomalies over,in episode highlight the limited presence of ENSO events. The occurrence of the dry episodes for all three regions is essentially random. With multi-centennial periods without an episode, and episodes at multi-decadal frequency at other miles. Following it discussion of possible mechanistic influences, it is concluded that stochastic forcing is responsible for the occurrence of dry episodes This Implies that there is no predictability associated with the initiation, duration or termination of individual (dry episodes This also suggests that the 2000-2007 dry episodes occurring over much of Australia may not be Caused by the greenhouse effect. Such an episode has a return period Of between 200 and 00 years based oil the mean frequency of occurrence in (lie present simulation Copyright (C) 2008 Royal Meteorological Society