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| Titel |
Tropical Indian Ocean Variability Driving Southeast Australian Droughts |
| VerfasserIn |
C. C. Ummenhofer, M. H. England, P. C. McIntosh, G. A. Meyers, M. J. Pook, J. S. Risbey, A. Sen Gupta, A. S. Taschetto |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250025673
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| Zusammenfassung |
| Variability in the tropical Indian Ocean has widespread effects on rainfall in surrounding
countries, including East Africa, India and Indonesia. The leading mode of tropical Indian
Ocean variability, the Indian Ocean Dipole (IOD), is a coupled ocean-atmosphere mode
characterized by sea surface temperature (SST) anomalies of opposite sign in the east and
west of the basin with an associated large-scale atmospheric re-organisation. Earlier work has
often focused on the positive phase of the IOD. However, we show here that the negative IOD
phase is an important driver of regional rainfall variability and multi-year droughts. For
southeastern Australia, we show that it is actually a lack of the negative IOD phase, rather
than the positive IOD phase or Pacific variability, that provides the most robust explanation
for recent drought conditions.
Since 1995, a large region of Australia has been gripped by the most severe drought in
living memory, the so-called “Big Dry”. The ramifications for affected regions are dire, with
acute water shortages for rural and metropolitan areas, record agricultural losses, the
drying-out of two of Australia’s major river systems and far-reaching ecosystem damage. Yet
the drought’s origins have remained elusive. For Southeast Australia, we show that
the “Big Dry” and other iconic 20th Century droughts, including the Federation
Drought (1895-1902) and World War II drought (1937-1945), are driven by tropical
Indian Ocean variability, not Pacific Ocean conditions as traditionally assumed.
Specifically, a conspicuous absence of characteristic Indian Ocean temperature
conditions that are conducive to enhanced tropical moisture transport has deprived
southeastern Australia of its normal rainfall quota. In the case of the “Big Dry”, its
unprecedented intensity is also related to recent above-average temperatures. Implications of
recent non-uniform warming trends in the Indian Ocean and how that might affect
ocean characteristics and climate in Indian Ocean rim countries are also discussed. |
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