Sub-daily rainfall events in an arid environment with marked climate variability: Variation among wet and dry years at Fowlers Gap, New South Wales, Australia

Abstract

The nature of rainfall events is explored through six years of below average rainfall, associated with negative Southern Oscillation Index (SOI), and three years of above average rainfall, associated with positive SOI (and strong La Niña conditions), at arid Fowlers Gap, Australia. There is a greater probability of rainfall in wet years, but the events themselves also change significantly. Rainfall depth per event was 116% larger on average in wet years than dry, and average event rainfall rate was 85% higher. However, these results are influenced by a small number of very large events in the wet years, and events of <2 mm occur at about the same rate in dry and wet years. Rainfall event profiles in dry years showed more Huff first quartile events likely to promote partitioning of rain into infiltration. In contrast, larger events in wet years showed a preponderance of Huff third quartile profiles likely to be associated with greater partitioning of rainfall into overland flow. This co-variation in rainfall event profile with annual rainfall, not previously described, is reasoned to increase the amplitude of ecological impacts of the SOI-related rainfall variability at this site.