Scientists have given the age we live in today a special geological name — the Anthropocene — an apt “buzzword” based on the premise that human beings are responsible for mass extinctions of plant and animal species, pollution of the oceans and an altered atmosphere. And this has to include our cities and how we build them.
Scientists at the Ecole Polytechnique Fédérale de Lausanne, using the city of Basel, Switzerland, found that the local weather was actually quite different in various parts of the city. They performed a variety of different simulations and discovered that the differences were due to the layout of the city’s buildings.
“Most city representations used in weather models are based on data obtained from tower measurements made at a particular location within the city, which current models approximate as a rough patch of land,” study author Marco Giometto said in the press release.
What he is saying is significant because when heat, humidity, and pollutants are computed using mathematical models, the results are based on an assumed “geometrically regular-shaped” city, and this is just not an accurate set of measurements because cities are not uniform in size and shape.
Giometto and his colleague, Andreas Christen, ran a 3-D simulation on Basel that showed how buildings create atmospheric turbulence, sucking up heat and pollutants into the atmosphere. To show how the wind moves around buildings, the scientists used “large-eddy simulations.”
By doing the wind simulations, they were able to see how the wind moves around buildings and this gave them a better picture of what really happens when storms and winds are impacting the city’s core. The scientists also showed just how incredibly crude our current weather modeling is in comparison.
A study in the Quarterly Journal of the Royal Meteorological Society this spring focused on Atlanta, Georgia’s unique urban geography and its role in the city’s unusually different weather. Keep in mind that a dense grid of buildings and pavement will make a city warmer. People living in apartments in New York City can attest to that.
But when that heat at street level is “kicked up” by tall buildings, choppy air patterns come into play. Then there are the aerosols and pollution during the day, which are usually higher, that have their role to play. This makes storms more likely during the week than on weekends.
Fast CoDesign.com made the observation that based on the results of the study, meteorologists could predict weather more accurately, and this would also apply to better use of the wind in saving energy.
Knowing this information could give new meaning to “city planning” in the future. Architects could design and set the shapes of buildings, align streets and open spaces, all to shape the weather in a city, even to our benefit.
“We need accurate computer simulations of the wind over cities to estimate dispersive terms for the prevailing wind directions,” says Giometto, according to Science News Online. “Ultimately, this information will allow us to develop accurate models, that will benefit urban residents.”
This interesting study, “Spatial Characteristics of Roughness Sublayer Mean Flow and Turbulence Over a Realistic Urban Surface,” was published in the Journal of Boundary Layer Meteorology.
