Summer storms are generally more frequent, intense and concentrated over cities than over rural areas, according to new, detailed observations of eight cities and their surroundings. The results could change how city planners prepare for floods in their cities, especially as urban areas expand and as climate change alters global weather patterns.
Summer storms are generally more frequent, intense and concentrated over cities than over rural areas, according to new, detailed observations of eight cities and their surroundings. The results could change how city planners prepare for floods in their cities, especially as urban areas expand and as climate change alters global weather patterns.
The new study finds that more storms form over urban areas and their boundaries than in surrounding areas, and that larger cities intensify rainfall more than smaller cities. The research was published in Earth’s Future.
« Cities are expected to become more populated and increase in size in the coming decades », said Herminia Torelló-Sentelles, an atmospheric scientist at the University of Lausanne and the study’s lead author. « Being able to quantify urban flood risk is important for urban planning and when designing urban drainage systems. »
The rain effect has been reported in studies of single cities, but the new research looked for trends and differences across multiple cities. Differences in urban rainfall patterns highlight the need to keep studying storm activity in cities across the globe, Torelló-Sentelles said.
Some storms have rain that falls evenly, like a sprinkler, while others drop rain in concentrated bursts, like a fire hose. The new study finds that cities can turn storms into fire hoses, dropping bursts of rainfall over small urban areas instead of spreading out the rain over a larger area. Those concentrated bursts of rainfall can exacerbate flood risks if city infrastructure cannot handle the deluge.
Most cities are producing more fire hose-like storms than rural areas. Cities are also spawning more storms than their surroundings, and bigger cities are generating stronger storms than smaller cities.
