Gaffney (1987) noted a number of shortcomings of the Bureau's drought alert system, some of which had been identified in a drought workshop in 1986 (Royal Meteorological Society, Australian Branch 1986). In particular, defining the start and end of droughts was complicated by the existence of strong seasonal variations in rainfall in some parts of the country. Gaffney proposed establishing specific criteria for droughts in different climatic zones. More complex systems for monitoring drought, taking more than decile rainfall into account, are now being established in various organisations.

Recently, the Bureau has developed a computerised national daily rainfall analysis system, based on the approximately 2000 rainfall reports received in 'real time'. Analyses of daily rainfall totals as well as monthly and seasonal analyses are prepared. These analyses provide more spatial detail than the district average rainfalls, and are available more quickly. The monthly and seasonal analyses can be compared with historical analyses (back to the start of the 20th century) which have been prepared using the same analysis technique. The Bureau's National Climate Centre provides these analyses, as well as analyses of monthly and seasonal temperatures, on the World Wide Web. New forms of drought monitoring and alerts can be based on these improved analysis systems.

Routine monitoring now has extended to the ocean, because of its influence on climate. The important role of the ocean in Australia's climate and economy is illustrated in Fig. 1. This shows the relationship between time-series of the value of Australian crops and sea-surface temperatures (Nicholls 1985) around northern Australia (for May-October, i.e., at the start of the 'crop year'). The figure shows changes in these variables from year to year, to remove trends due to changes in technology. The close relationship is very clear, with a correlation of 0.65 (n=44; significant at 0.1%). The Bureau has developed an operational system for preparing operational analyses of global sea-surface temperatures, and an objective system for the operational analysis of tropical subsurface thermal structure (Smith 1995). These systems are run operationally and provide much of the detailed information regarding the current behaviour of the El Niņo—Southern Oscillation. These analyses, plus analyses of southern hemisphere atmospheric circulation, are published in the Climate Monitoring Bulletin Australia, distributed every month since February 1986. They provide input to the operational seasonal climate prediction.

Bureau of Meteorology