May 27, 2011 13:50 GMT  ·  By
Major urban center change the properties of thunderstorms passing over, making the latter more violent to settlements downwind
   Major urban center change the properties of thunderstorms passing over, making the latter more violent to settlements downwind

Scientists with the Purdue University say that large urban concentrations are known to cause disturbances in massive thunderstorms hitting them. Their newest research demonstrates that the areas located downwind from these cities experience the effects of these modifications.

If passing over a city changes the structure or type of clouds in a thunderstorm, then the effects of this substitution will be felt most intensely in areas downwind from the city, where the changes will have time to take effect, the group argues.

Most often, cities make storms stronger and more violent, priming them to cause devastation as they pass over the urban centers and go on their way. These conclusions are based on 10 years of relevant, scientific data.

Purdue associate professor of agronomy and earth and atmospheric sciences Dev Niyogi, the leader of the work, was the one who collected the data, which spanned the Indianapolis metropolitan area.

Using the datasets at his disposal, the researcher began analyzing how storms tended to change as they approached the urban area. Sure enough, he soon discovered a trend rearing its ugly head from the data.

“About 60 percent of the daytime thunderstorms seem to change their characteristics. Before the storms approach the urban area, we see them as a more organized line of storm cells,” the expert says.

“As the storms get past the urban area, there are smaller but more cells, signifying splitting. So, quite often, we see storms approach the city, split around it and come back together on the other side to create a more intense storm,” he goes on to add.

Niyogi is the lead author of a new scientific study detailing the findings, which was published in the latest issue of the Journal of Applied Meteorology and Climatology. The expert is also Indiana's state climatologist.

“Interestingly, the storms only appeared in the model simulations when the Indianapolis urban area was present. This shows that the urban area can help create an environment that can at times trigger storms,” Niyogi says.

He explains that the reasons why storms are changed are multiple. They include the altering of natural wind patterns on account of the small building, and higher temperatures caused by head and pollution.

“What the storm is really responding to is those changes in the environment. All three of those – the change in landscape from rural to urban, heat and particulates – in some way affect the environment around the city,” the Indiana expert concludes.