Rainfall change in central Australia, 1920-2013

Abstract

The interior of Australia experiences low average and highly variable rainfall, which influences its ecological and cultural significance. This variability stems from the numerous climatic drivers affecting the subtropics; these have been influencing rainfall declines in the south-east and south-west, and rainfall increases in the north-west, over the past 30–50 years. To investigate if such shifts have occurred in central Australia this thesis examined the timing and characteristics of rainfall shifts in the region between 1920 and 2013, as well as which climatic drivers may be influencing these shifts. Breakpoint analysis was used to establish when rainfall shifts occurred, using the AWAP and GPCC datasets, while breakpoint analysis and correlation maps were used to examine the influence of five drivers (ENSO, subtropical ridge latitude and pressure, IOD and SAM) and pressure and wind patterns on these shifts. A shift to increased annual, summer and spring (summer and autumn) rainfall and variability was found in the early 1970s (1990s), and a shift to increased winter rainfall variability in 1954. Multiple climatic drivers influenced each of these shifts: in the 1970s, the IOD (summer) and ENSO (spring); in the 1990s, changes in the relationship with the subtropical ridge (both seasons); and for 1954, changes in the ENSO, IOD and subtropical ridge. Long-term rainfall increases were also found, influenced by changes in pressure and winds over the Southern Ocean and a corresponding positive trend in the SAM, and/or the strengthening of the northern subtropical jet. These changes have undoubtedly impacted human activities and ecosystems in the region, and will continue to do so in future. Show more