Micro and macro urban heat islands in an industrial city: Bradford, UK

The urban heat island (UHI) phenomenon refers to the temperature difference(s) between urban/built environments and suburban/natural areas. It affects energy use, health, water quality, and in brief, the quality of life in cities. Understanding the magnitude of this issue could help urban planners and decision makers to better implement green interventions into their cities. This paper shows the results of field measurements carried out to study the UHIs in Bradford, as one of the most deprived cities in the UK with minimum green infrastructure. In the first phase of the study, air temperatures were measured in twenty locations (four areas) with different land covers in Bradford. These measurements were called micro UHI study, as the air temperatures were measured in areas within the boundaries of the city. Data were collected in late summer and early winter. The results showed that the UHI is more sensible in the colder day (with average 0.6 °C cooler air temperature in a green area compared to the city centre). Greener areas experienced higher wind and lower air temperatures compared to dense urban settings in December. In the second phase of the study (macro scale), diurnal air temperatures from a residential (urban) versus a rural site were compared during a heat wave episode (seven days). It was observed that the rural site was 0.8 °C cooler than the residential/urban site. The maximum temperature differences occurred during the nights/early mornings between the two sites (3.2 °C at 5:00am).