On the Link Between Physical Aridity and Rainfall Intermittency

Rainfall intermittency is a defining characteristic of the hydrology in arid and semi-arid regions. These climates experience prolonged droughts interrupted by brief, intense rainfall events, which have substantial effects on landforms, ecosystems, and water resources. Under climate change, intermittent precipitation patterns are expected to become more prevalent across a wider range of climates. Despite this, there is limited research on the link between rainfall intermittency and physical aridity. Furthermore, high-resolution representation of rainfall variability remains a significant source of uncertainty in rainfall modeling and downscaling. Herein, we investigate the relationship between rainfall intermittency, its temporal scaling behavior, and aridity from a climatological standpoint. We hypothesize that intermittency is shaped by fine-scale processes, such as land-atmosphere interactions and local water and energy dynamics, alongside large-scale atmospheric forces. By analyzing extensive hourly and sub-hourly precipitation datasets from the Contiguous United States (NOAA US-HPD) and Australia (Australian Bureau of Meteorology), we uncover a clear functional relationship between intermittency and aridity metrics across diverse water-limited climates. These findings offer a foundation for enhancing precipitation downscaling techniques and understanding future precipitation regimes in regions with limited water availability.