Wednesday, 15 January 2025: 2:45 PM
221 (New Orleans Ernest N. Morial Convention Center)
Localized extreme rainfall events challenge weather forecasting in urban areas like Chicago, where complex surface conditions and local climate effects significantly influence storm behavior. This study examines how specific urban characteristics—such as heat fluxes, surface roughness, and turbulence—interact with incoming convective storms and shape the differences in hydrologic responses. By exploring these interactions, we aim to understand how urban environments contribute to variations in localized extreme rainfall and flood risks across different storm types.
We focus on key thermal effects—Urban Heat Island (UHI), moisture availability, and heat fluxes—and turbulent effects—surface roughness, wind patterns, and convergence zones—that modify atmospheric stability and storm dynamics. These factors are crucial for understanding how urban environments influence extreme rainfall events. Through the analysis of thermal and turbulent indicators, correlation, and PCA, we identify dominant urban factors contributing to extreme rainfall in Chicago. Additionally, a climatological analysis of both MCSs (Mesoscale Convective Systems) and isolated smaller-scale convective storms reveals how urban conditions may alter storm intensity and rainfall distribution.
Finally, we compare the hydrologic responses to different storm types, emphasizing the contrasting impacts of isolated storms and organized MCSs. Isolated storms, more sensitive to urban-induced effects, often result in intense, localized rainfall leading to flash flooding, while MCSs, with their broader rainfall patterns, can exacerbate widespread and prolonged flooding. This comparative analysis highlights the importance of integrating urban-induced effects into forecasting models to enhance prediction accuracy and improve urban flood management in cities like Chicago.
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