The influence of urban reconstruction in urban heat island effect: Cangxia area of Fuzhou City, China

The urban development is usually accompanied with the re-planning and reconstruction of the old urban area, which is one of the key issues of the urban development program. Over the past decade, Fuzhou City of Fujian province, SE China, has speeded up its reconstruction progress. The Cangxia area, located in the southwestern of the city, was replaned and reconstructed to improve people's living conditions because the area was full of intensively-built squatter settlements. In order to study the thermal environmental changes of the Cangxia area before and after the reconstruction, three Landsat TM images of 1986, 1996 and 2006 were utilized to perform feature extractions of the thermal-related information of the area, such as the land surface temperature (LST), impervious surface area (ISA) and vegetation coverage. The quantitative analysis on the relationship between ISA and LST suggested a positive exponential relationship between the two factors. With the assistance of the Urban-Heat-Island Ratio Index (URI), the digital image processing on the three multi-temporal images revealed the spatial and temporal variations of the urban heat island (UHI) effect in the investigated area from 1986 to 2006. The results showed that after the launch of the reconstruction project of this squatter settlement-dominated area, the UHI effect in the area had been greatly mitigated in the past 20 years, since the URI value had been decreased from 0.648 in 1986 to 0.245 in 2006. This owes greatly to the significant decrease in high-density ISAs and the notable increase in vegetation covers. The reconstruction is of benefit to the UHI mitigation of the Cangxia area.