SCIENCE OF SEASONAL CLIMATE PREDICTION
Towards more valuable seasonal climate forecasts for farmers
by Peter McIntosh, CSIRO Marine and Atmospheric Research
Dr Peter McIntosh is a Principal Research Scientist in oceanography and climate with CSIRO Marine and Atmospheric Research in Hobart, where he has worked for 17 years. Prior to that he worked with the Bureau of Meteorology Research Centre in Melbourne. He has a PhD in Applied Mathematics and Oceanography from Monash University.
Two approaches to obtaining more valuable seasonal climate forecasts for farmers are described. The first involves obtaining a better understanding of the climate system by exploring the individual weather events that make up seasonal climate. A synoptic decomposition of rainfall events in North-West Victoria (Pook et al. 2006) indicates that there is one dominant synoptic system that is responsible for the majority of useful rainfall: the cutoff low. The seasonal frequency and intensity of these systems are then related to large-scale atmospheric and oceanic patterns. In addition, the sources of moisture and uplift necessary for rainfall are explored using a backward air-parcel tracking technique. The moisture source is found to be quite variable spatially, but is most likely to be from the oceans north of Australia. The number and strength of cutoff lows appears to be controlled by ocean temperatures to the south, and possibly also land temperatures. Vertical motion is also shown to be an essential part of the rainfall process.
The second approach involves simulation of the growth of a wheat crop in North-West Victoria, and examination of the application and potential value of different forecast systems. The importance of assessing on-farm value accurately using cross-validation techniques (McIntosh et al. 2005) is highlighted. It is concluded that a system to forecast rainfall might have some value provided it is accurate enough (Moeller et al. 2006). However, this might not be the best way forward, as it might only capture a modest fraction of the potential benefit of a forecast.
References
McIntosh P C, Ash A J and Stafford Smith M (2005). From oceans to farms: Using sea-surface temperatures in agricultural management. J. Clim. 18, 4287-4302.
Moeller C, Smith I, Asseng S, Ludwig F and Telcik N (2006). Assessing the economic value of seasonal climate forecasting – case studies from the wheat-belt in Western Australia’s Mediterranean region. (Submitted to Agric. Forest Met.).
Pook M J, McIntosh P C and Meyers G A (2006). The synoptic decomposition of cool season rainfall in the south-eastern Australian cropping region. J. Applied Met. Clim. (in press).
