Abstract
The effect of the expansion of urban impervious surfaces on surface urban heat islands (UHIs) has attracted research attention due to its relevance for studies of local climatic change and habitat comfort. In this study, using five satellite images of Xiamen city, Southeast China (four images from the Landsat 5 Thematic Mapper (TM) and one from the Landsat 8 Operational Land Imager/Thermal Infrared Sensor (OLI/TIRS)) acquired in summer between 1989 and 2016, together with spatial statistical methods, the changes in impervious surface area (ISA) were investigated, the spatiotemporal variation of the intensity of urban heat islands (UHIs) was explored, and the relationships between land surface temperature (LST) and the percentage of impervious surface area (ISA%), the normalized difference vegetation index (NDVI), and fractional vegetation coverage (Fv) were investigated. The results showed the following: (1) According to the biophysical composition index (BCI) combined with an ISA post-processing method, Xiamen has witnessed a substantial increase in ISA, showing a 6.1-fold increase from 1989 to 2016. The direction of ISA expansion was consistent throughout the study period in each of the five districts of Xiamen; (2) a bay-like UHI form is observed in the study area, which is remarkably distinct from the central-radial UHI form observed in previous studies of other cities; (3) the extent of UHIs in Xiamen greatly increased between 1989 and 2016, experiencing a 4.7-fold increase in UHI areas during this time. However, during the same period, the urban heat island ratio index (URI)—that is, the ratio of UHI area to ISA—decreased slightly. The UHI area decreased in some urban parts of Xiamen due to a significant increase in vegetation coverage, urban village redevelopment, and the construction of new parks; (4) sea ports and heavy industrial zones are the greatest contributor to surface UHI, followed by urban villages; and (5) LST is strongly positively correlated with ISA%. Each 10% increase in ISA was associated with an increase in summer LST of 0.41 to 0.91 K, which compares well with the results of related studies. This study presents valuable information for the development of regional urban planning strategies to mitigate the effects of UHIs during rapid urbanization.
Highlights
Over the past several decades, urbanization has progressed at an unprecedented rate throughout the world [1]
This study focused on the changes in ISA, investigated the area and intensity of urban heat islands (UHIs), and revealed the relationships between land surface temperature (LST) and (1) the percentage of impervious surface area (ISA%), (2) the normalized difference vegetation index (NDVI), and (3) the fractional vegetation cover (Fv)
The results show that the ISA in Xiamen city increased dramatically over the study period, from 63.06 km2 in 1989 to 447.04 km2 in 2016, a net increase of 384.01 km2 (Figure 2)
Summary
Over the past several decades, urbanization has progressed at an unprecedented rate throughout the world [1]. In 1950, only 29% of the global population lived in urban areas; by 2018, this proportion was 55%. Urbanization inevitably involves the transition from natural vegetation coverage to impervious surfaces (e.g., paved roads, building roofs, and parking lots) [5]. It brings great social and economic benefits, urbanization leads to a number of environmental issues, such as urban heat islands (UHIs), the degradation of water quality, and loss of biodiversity [6]. Remote sensing technology can be used to obtain detailed images of land cover with a high temporal resolution, allowing a synoptic and uniform means of mapping urban impervious areas and studying the effects of surface UHIs [10]
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