Interannual variability in rainfall and wet spell frequency during the New South Wales sugarcane harvest season

Abstract

The sugarcane harvest season in northern New South Wales (NSW), Australia operates from June to November. Rainfall during this period can delay harvest practices and push the harvest window into the wetter summer period which can have severe economic consequences for industry. Farmer groups acknowledge that, whilst information about seasonal rainfall totals can assist forward planning activities impacted by harvest rainfall, knowledge about the number of wet spells during the harvest season would also be helpful. This diagnostic study investigated the interaction between harvest rainfall totals and wet spell frequency for Harwood, a major sugarcane growing region in Northern NSW. The El Nino-Southern Oscillation (ENSO) effect on harvest rainfall totals and wet spell frequency was also considered and climate diagnostics for extreme wet seasons were investigated. A moderate linear relationship between total rainfall and wet spell frequency exists for both winter (r = 0.68) and spring (r = 0.66). The ENSO had little influence in winter but La Niña events in spring favoured higher rainfall totals and wet spell frequency. Extreme wet seasons were largely influenced by positive pressure anomalies over southeastern Australia and the Tasman Sea.