This report investigates the effect of changes in the number of rainy days, the amount of rain that falls on rainy days or a combination of the two on the inter-annual variations in Queensland rainfall. The objective is to determine the association between climate drivers and the occurrence of rainfall in Queensland. Analysis of this relationship will enable focusing on the impact of those drivers that influence the key portions of the rainfall distribution in Queensland by using this information and knowledge to predict how these drivers will influence the occurrence of rainfall in a changing climate. Understanding the frequency and magnitude of these phenomena can significantly improve societal resilience.
Knowledge of the relationship between climate drivers and occurrence of rainfall allows for a better understanding of global climate model outputs. The future analysis of key climate drivers for Queensland rainfall variability depends on which of these drivers affect the key portions of the rainfall distribution that are variable on inter-annual temporal scales. Because of limited horizontal resolution global climate models are not able to capture observed distribution of rainfall intensity particularly for intense rainfall. However, if the models are able to capture the observed frequency of rainfall in Queensland, then this information could be used to assess the inter-annual variability of rainfall amounts in these models. Focusing attention on changes in the frequency and intensity of Queensland rainfall in association with global and regional climate phenomena will help understand how these drivers will influence rainfall occurrence in future.
The gridded SILO rainfall dataset was analysed for 1900-2008. Analysis was performed on the November-April half-year, as this period accounts for at least 80% of the annual rainfall in Queensland. Several thresholds of rainfall were used to define a "rainy day": 5 mm/day, 10 mm/day, 25 mm/day and 50 mm/day
