Geneva: The features that make cities unique can help in understanding how they affect weather and disperse air pollutants, a new study has found. Compared to their surroundings, cities can be hot enough to influence the weather, researchers said.
Industrial, domestic and transportation-related activities constantly release heat and after a warm day, concrete surfaces radiate stored heat long into the night. These phenomena can be strong enough to drive thunderstorms, they said.
According to scientists, it is not only about the heat cities release; it us also about their spatial layout. By channelling winds and generating turbulence hundreds of metres into the atmosphere, the presence and organisation of buildings also affect weather and air quality.
Researchers led by Ecole Polytechnique Federale de Lausanne (EPFL) in Switzerland have shown that the way cities are represented in today’s weather and air quality models fails to capture the true magnitude of some important features such as the transfer of energy and heat in the lower atmosphere.
They also found that processes that atmospheric sensors are unable to sense are essential to more accurately represent cities in weather models.
When wind blows over a city, buildings interact with the moving air mass, generating turbulence, much like sticking your fingertips into a stream causes visible vortices to form on the water surface, researchers said.
This turbulence spreads up into the atmosphere and down into the streets. As a result, more heat, humidity and pollutants are transported upwards from the ground.
