The London Heat Island – surface and air temperature measurements in a park and street gorges

This paper reports results from short-term tests carried out as part of a project to characterize the urban heat island in London. The investigations looked at air temperatures upstream and downstream of a park and the surface and air temperatures within street gorges. It was found that the air in the park was associated with lower mean (0.6°C [1.1°F] less) and peak temperatures (1.1°C [2.0°F] less) compared to residential or shopping streets on either side. The apparent cooling influence of the park extended downstream between 200 and 400 meters (200 to 400 yards). Measurements in four street gorges showed a wide variation in surface temperatures—up to 22°C (40°F)—although 5ºC to 10°C (9ºF to 18°F) was more typical. For a given façade, lighter surfaces were associated with lower temperatures, between 6ºC and 10°C (11ºF and

18°F) cooler. A strong relationship was found between mean gorge surface temperature and the gorge air temperature measured at 6 m (20 ft) (half-gorge height). This was true for both a sunny day and a cloudy day. The results suggest that significant reductions in air temperature may be possible by adjusting the albedo of urban surfaces.