Urban Rainfall Anomalies: Regional and Diurnal Variability under Diverse Landscapes

Urbanization influences regional climates and extreme weather. Previous studies have documented rainfall modification due to urbanization as a climatology or for storm cases. Whether there is any diurnal signature to urban precipitation anomalies, and whether this varies across various landscapes remains poorly understood. Analyzing rainfall data for 175 US cities, we found that most cities experience more intense extreme precipitation compared to their rural backgrounds. Inland cities exhibit strong urban precipitation enhancement during summer afternoons, and the pattern varies with urban heat islands and winds. Under weak wind conditions, cities can see 10% more summer afternoon rainfall. Coastal cities, under the influence of sea-land breeze, experience 3.5 times amplified daily urban precipitation enhancements relative to inland cities. Urban impacts are also noted for mountain cities, affecting their topography-dominated precipitation patterns. This study enhances our understanding of urban climates and has implications for developing climate adaptation and future infrastructure designs.