Abstract
The combined usage of high-resolution satellite images and thermal infrared (TIR) data helps understanding the thermal effect of urban fabric properties and the mechanism of urban heat island (UHI) formation. In this study, three typical urban functional zones (UFZs) of downtown Shanghai were chosen for quantifying the relationship between fine-scale urban fabric properties and their thermal effect. Nine land surfaces and 146 aggregated land parcels extracted from a QuickBird image (dated 14 April 2014) were used to characterize urban fabric properties. The thermal effect was deduced from land surface temperature (LST), intra-UHI intensity, blackbody flux density (BBFD) and blackbody flux (BBF). The net BBF was retrieved from the Landsat 8 TIR band 10 dated 13 August 2013, and 28 May 2014. The products were resampled to fine resolution using a geospatial sharpening approach and further validated. The results show that: (1) On the UFZ level, there is a significant thermal differential among land surfaces. Water, well-vegetated land, high-rises with light color and high-rises with glass curtain walls exhibited relatively low LST, UHI intensity and BBFD. In contrast, mobile homes with light steel roofs, low buildings with bituminous roofs, asphalt roads and composite material pavements showed inverse trends for LST, UHI intensity, and BBFD; (2) It was found that parcel-based per ha net BBF, which offsets the “size-effect” among parcels, is more reasonable and comparable when quantifying excess surface flux emitted by the parcels; (3) When examining the relationship between parcel-level land surfaces and per ha BBF, a partial least squares (PLS) regression model showed that buildings and asphalt roads are major contributors to parcel-based per ha BBF, followed by other impervious surfaces. In contrast, vegetated land and water contribute with a much lower per ha net BBF to parcel warming.
Highlights
To date, intensive human activities and anthropogenic climate change occurring across local, regional, and global scales have increasingly attracted concern [1,2,3]
The Landsat 8 thermal infrared (TIR) band data acquired on 13 August 2013 and 28 May 2014 were used for retrieval of land surface temperature (LST), intra-urban heat island (UHI) intensity, blackbody/sensible heat flux density (BBFD), blackbody/sensible heat flux (BBF), and net blackbody flux (BBF)
We presented the differential thermal effect of urban fabric properties, i.e., LST, UHI intensity and blackbody flux density (BBFD) associated with varying land surfaces at urban functional zones (UFZs) level
Summary
Intensive human activities and anthropogenic climate change occurring across local, regional, and global scales have increasingly attracted concern [1,2,3]. Since the 1970s, satellite-based thermal remote sensing has been an important approach for characterization of the impact of local and regional climate change induced by intensive human activities, in particular modification of urban climate [11,12,13]. High-resolution TIR data, such as Landsat ETM+ (60 m) and ASTER (90 m) TIR data, were used with downscaling methods to sharpen coarse-resolution (more than 100 m) land surface temperature (LST) data to produce finer LST maps and enhance their application in regional thermal monitoring [17,18,19]. Existing downscaling algorithms, which were developed for sharpening images over rural and natural areas, have large errors when applied in urban areas [20]
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