Study find US Thunderstorms Preferentially Initiated over Cities

Tuesday 03rd Mar 2015 by theWeather Club

A recent study conducted in the US has shown that thunderstorms can be preferentially initiated over cities in southeast USA. The research, published in the Quarterly Journal of the Royal Meteorological Society, used radar reflectivity data to explore where isolated thunderstorms initiated during 1997-2013. 

The long-term dataset revealed that such events occur more often over urban areas compared to surrounding rural areas. This suggests that man-made changes to land-use and urbanisation in humid, subtropical locations can lead to the development of more thunderstorms over and downwind of developed areas. This is particularly notable in late afternoon and early evening during the summer months. Furthermore, thunderstorm initiation over cities was also significantly higher on weekdays compared to weekends, suggesting that man-made pollutants - higher during the traditional working week - may enhance development.

"Urbanization has led to more thunderstorm initiation events than would have occurred over natural vegetation. These events, which are an illustration of anthropogenic climate change at the local scale, can produce a number of dangerous weather hazards including lightning, strong winds, hail, and flash floods, often with little or no warning," said Alex Haberlie, lead author of the study.

"City planners, meteorologists, and citizens who live in or near a large urban area should be aware of this increased risk."

The influence of urban areas on clouds and precipitation is a topic that has been the subject of extensive research and speculation in the past. The complexity of factors influencing precipitation development and the difficulty in determining precise triggers, has resulted in conflicting findings. This study certainly adds to our understanding of the effect urban areas have on convective precipitation development.