Multi-timescale-based precipitation concentration dynamics and their asymmetric impacts on dry and wet conditions in a changing environment

Precipitation is one of the most important climatic factors affecting the natural environment and hydrological processes. The excessive concentration of precipitation at different time scales in spatial and temporal distribution could increase the possibility of floods or droughts and their disaster-causing extent in a changing environment. Nevertheless, the dynamics of precipitation concentration and its specific effects on dry and wet conditions remain unknown. To this end, the precipitation concentration indexes of different time scales was adopted to characterize the non-uniform distribution of precipitation within the year in this study, and the spatial and temporal variation characteristics of precipitation concentration was examined. The impacts of precipitation concentration dynamics on dry and wet conditions were then quantified based on the conditional probability of dry and wet conditions when unusual concentration of precipitation events occur under different scenarios. The Weihe River basin, the largest tributary of the Yellow River in China, was selected as a case study. The results show that: (1) daily concentration index (CID), monthly concentration index (CIM), and precipitation concentration degree (PCD) are higher in the north part of the basin and show an insignificant increase trend, the precipitation distribution in the region is extremely non-uniform, and the risk of floods and droughts is increasing; (2) in the same scenario, CIM has the strongest impact on dry conditions, followed by CID and finally PCD, PCD has the strongest impact on wet conditions, followed by CID and finally CIM; (3) under different scenarios, as CID, CIM and PCD increase, the probability of dry conditions gradually decreases, while the probability of wet conditions gradually increases; (4) precipitation concentration shows an asymmetric impact on drought and wet conditions. In general, this study provides new insights into the precipitation concentration dynamics and their asymmetric impacts on dry and wet conditions, which is highly relevant for drought and flood prevention.