Interannual to Decadal Prediction of Terrestrial Precipitation Using Sea Surface Salinity as a Precursor - Case Study of Australian Rainfall

Saurabh Rathore, Institute for Marine and Antarctic Studies, University of Tasmania, Taroona, TAS, Australia, Nathaniel L. Bindoff, University of Tasmania, Institute for Marine and Antarctic Studies, Hobart, TAS, Australia, Caroline Ummenhofer, WHOI, Woods Hole, United States, Helen Elizabeth Phillips, Institute for Marine and Antarctic Studies, University of Tasmania, Hobart, TAS, Australia and Ming Feng, CSIRO, Environment, Crawley, Western Australia, Australia
Abstract:
Oceans are the dominant component of the global water cycle and serve as the largest source for atmospheric moisture that results in precipitation over land. The moisture exchange process between the ocean and atmosphere through evaporation leaves an imprint on the sea surface salinity (SSS). This variation in SSS, in conjunction with atmospheric moisture flux, enables us to locate the oceanic source of moisture for precipitation over land. Moreover, the interannual to decadal variations of the SSS show the corresponding signatures in the terrestrial precipitation. In this study, we use singular value decomposition analysis (SVD) to demonstrate that the interannual to decadal variations of the prior season (July-September and September-November) SSS in the Indo-Pacific warm-pool covaries with the summer (December-February) rainfall of Australia. We show that on interannual timescales, summer rainfall in north-western to central Australia is linked with the prior season variations in SSS of the Indo-Pacific warm pool. On decadal timescales, the spells of high and low rainfall in eastern Australia are linked with the decadal modulation of SSS in the western Pacific. Finally, we show that the extreme precipitation events of Australia (Brisbane flood of 1973-74 and 2010-11) are strongly correlated with anomalously high prior season SSS in the Indo-Pacific warm pool. This anomalously high prior season SSS is accompanied by a moisture flux that converges over Australia in the subsequent summer season. We demonstrate that both interannual and decadal variations of SSS in the Indo-pacific warm pool affect the seasonal prediction of rainfall over Australia. Our study builds on previous work in other countries and raises the possibility of SSS being a skillful predictor of terrestrial rainfall over Australia on interannual to decadal time scales.
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