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Probabilistic forecasts of the onset of the north Australian wet season

Lo, F. and Wheeler, M.C. and Meinke, H. and Donald, A. (2007) Probabilistic forecasts of the onset of the north Australian wet season. Monthly Weather Review, 135 (10). pp. 3506-3520.

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Article Link(s): http://dx.doi.org/10.1175/MWR3473.1

Publisher URL: http://www.ametsoc.org/

Abstract

The amount and timing of early wet-season rainfall are important for the management of many agricultural industries in north Australia. With this in mind, a wet-season onset date is defined based on the accumulation of rainfall to a predefined threshold, starting from 1 September, for each square of a 1° gridded analysis of daily rainfall across the region. Consistent with earlier studies, the interannual variability of the onset dates is shown to be well related to the immediately preceding July-August Southern Oscillation index (SOI). Based on this relationship, a forecast method using logistic regression is developed to predict the probability that onset will occur later than the climatological mean date. This method is expanded to also predict the probabilities that onset will be later than any of a range of threshold dates around the climatological mean. When assessed using cross-validated hindcasts, the skill of the predictions exceeds that of climatological forecasts in the majority of locations in north Australia, especially in the Top End region, Cape York, and central Queensland. At times of strong anomalies in the July-August SOI, the forecasts are reliably emphatic. Furthermore, predictions using tropical Pacific sea surface temperatures (SSTs) as the predictor are also tested. While short-lead (July-August predictor) forecasts are more skillful using the SOI, long-lead (May-June predictor) forecasts are more skillful using Pacific SSTs, indicative of the longer-term memory present in the ocean.

Item Type:Article
Additional Information:© American Meteorological Society.
Keywords:Cape York; central Queensland; climatological forecasts; early wet season rainfall; north Australia; Southern Oscillation Index (SOI); Top End; tropical Pacific sea surface temperatures (SSTs).
Subjects:Science > Statistics
Agriculture > Agriculture (General) > Agricultural meteorology. Crops and climate
Deposited On:25 Feb 2009 03:57
Last Modified:17 Nov 2010 00:13

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