Spatial and temporal patterns of precipitation concentration and their associated risks

Global climate change has profoundly altered precipitation distribution patterns, with the "Wet getting Wetter, Dry getting Drier" (WWDD) pattern widely recognized. However, most previous studies have addressed either the temporal or spatial dimensions of precipitation concentration in isolation, leaving a critical gap in understanding their finer-scale changes and their combined effects and interactive risks. Here, we use the Gini coefficient and ERA5-Land daily data (1951-2020) to assess global precipitation concentration in both time and space. Based on long-term trends, we classify regions into WWDD or WDDW patterns. Our results reveal that 46.4% of global land area shows increasing spatial concentration (WWDD), while 67.4% shows increasing temporal concentration (WWDD). Notably, 33.6% of the global land area exhibits a WWDD pattern in both spatial and temporal dimensions. These jointly concentrated regions are especially vulnerable, as precipitation is becoming more uneven in both time and space, increasing the risk of floods, droughts, and other extreme hydrometeorological events. In contrast, regions with increasing concentration in only one dimension may face more specific hazards-such as short-duration intense precipitation or localized runoff surges. These findings have important implications for assessing global precipitation concentration and informing hydrological disaster management strategies.