Extreme daily rainfall has intensified and become more frequent globally. However, in Australia, long-term changes in the characteristics of extreme rainfall are not well understood. Commonly used indices that examine the characteristics of rainfall rarely show statistically significant long-term historical changes in mean and extreme rainfall events. Here we use a rainfall event-based approach to study observed changes in intensity and frequency of rainfall events in Australia. This approach defines rain events as n consecutive days of rain to account for varying event duration. The intensity of a rainfall event is defined as the average of the daily accumulation of rainfall over the event duration. We find that short-duration rainfall events (1–2 day) have become more frequent and have intensified in large parts of Australia since the beginning of the 20th century. The frequency of longer duration rainfall events (3–4 day and 5–6 day) show substantial and statistically significant reductions in the south of Australia and increases in some parts of northern Australia. The frequency of rainfall events lasting >6 days has increased in the north and decreased in the south. The robust increase in short-duration episodic rainfall events across Australia and decrease in the frequency of extended episodic events imply rainfall has become more sporadic in Australia. Changes in rainfall intensities are less consistent compared to changes in frequency across the continent. We find an increase in intensity in the 1–2 and 3–4 day events, but the trends in the intensity of those events lasting >4 days are mostly not significant. Overall, changes in the characteristics of rainfall events of duration n days provide more spatially coherent results than those presented previously.

每天的极端降雨加剧并且在全球范围内变得更加频繁。但是，在澳大利亚，人们对极端降雨特征的长期变化了解不多。常用的检查降雨特征的指标很少显示出在平均和极端降雨事件中具有统计意义的长期历史变化。在这里，我们使用基于降雨事件的方法来研究观察到的澳大利亚降雨事件强度和频率的变化。这个方法规定降雨事件为ñ连续下雨天以解释事件持续时间的变化。降雨事件的强度定义为该事件持续时间内每日降雨累积的平均值。我们发现，自20世纪初以来，短期降雨事件（1-2天）变得更加频繁，并在澳大利亚大部分地区加剧。持续时间较长的降雨事件（3-4天和5-6天）的频率在澳大利亚南部显着减少，并且在统计上具有显着意义，而在澳大利亚北部某些地区则有所增加。持续超过6天的降雨事件的频率在北部增加，而在南部减少。在澳大利亚，短时突发性降雨事件的强劲增加和突发性事件的发生频率的降低意味着澳大利亚的降雨变得更加零星了。与整个大陆的频率变化相比，降雨强度的变化不太稳定。我们发现1-2天和3-4天事件的强度增加，但是持续时间超过4天的事件强度的趋势大部分并不显着。总体而言，历时降雨事件特征的变化n天比以前提供的结果在空间上更连贯。