Seasonal Forecast and Climate Variability

Relationships between sea surface temperatures and climate are well documented. The relationship between Australia's hydroclimate and the El Niño/Southern Oscillation (ENSO)

Australia World

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Mean annual runoff (mm)

The L-Cv is used as a measure of inter-annual runoff variability.

It is a measure of relative variability similar to the coefficient of variation (standard deviation divided by the mean).

The L-Cv in the plot are for catchments in the Cfb Koppen climate type, which represents a temperate climate.

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Figure 1 Interannual variability of Australian streamflow relative to the rest of the world.

is among the strongest in the world (Chiew and McMahon, 2002). El Niño describes the warm phase of a naturally occurring sea surface temperature oscillation in the tropical Pacific Ocean. Southern oscillation refers to a seesaw shift in surface air pressure at Darwin, Australia, and the South Pacific island of Tahiti. Several indices have been derived from this relationship, in particular the Southern Oscillation Index (SOI), which describes the Tahiti minus Darwin sea level pressure and is commonly used as an indicator of ENSO. The strong relationships that exist between climate, streamflow, and ENSO form the scientific basis for forecast tools developed throughout Australia and other parts of the world. In the Australian context, the Bureau of Meteorology routinely provides seasonal climate outlooks (e.g., probability that the total rainfall over the next 3 months will exceed the median) and computer packages such as Rainman Streamflow (Clewett et al., 2003) are heavily promoted. The patchy adoption of these tools, and thus the inability to reap the perceived gains in water use efficiency, is of concern to their promoters and research and development agencies.

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