on Oct 6th, 2006
Wind and Breaking Umbrellas
It’s a common site when it starts to rain strongly. On the side of the road are abandoned umbrellas torn apart by the force of the wind. Unfortunately, today, my umbrella was among the casualties, though fortunately it happened right as I arrived at work so I didn’t get too when. It started me thinking about the effect that builds have on the wind in cities. Certainly, if we were in a typhoon many broken umbrellas would be normal. But this was just an ordinary rain storm and the umbrellas were generally grouped in the same place. The placement was not for garbage clean-up but at the base of the larger buildings in the district. As I walked though I noted that the wind patters got pretty erratic around the larger buildings, but not so much around the lower development. The reason is that tall buildings play havoc with the wind flow. Tall buildings can create strong unpredictable wind at the base because the wind is being forced down as it comes in contact with the side of the building. At the case this can be felt as very strong gusts of wind that can suddenly change in direction. In places where there are long straight pieces of road with many tall buildings on both sides, this can create some very strong wind that races down the corridor.
Wind effects (at least those at the base) seem to be largely ignored in building and city design. This seems to have changed in recent years as cities come to realize that they can use wind to their advantage in alleviating the “heat island” effect. In Tokyo、for example, when the Tokyo station are buildings are going to rebuilt, letting the wind though to cool the center for the city a bit more. Recent studies also showed that the hottest areas of Tokyo were not necessarily those that were the most build-up (which all happen to be fairly close to water) but some of the more inland areas turned out the be very hot.