Abstract
Conspicuous expansion and intensification of impervious surfaces accompanied by rapid urbanization are widely recognized to have exerted evident impacts on the urban thermal environment. Investigating the spatially and temporally varying relationships between Land Surface Temperature (LST) and impervious surfaces (IS) at multiple scales is of great significance for steering IS expansion and intensification. This study proposes an analytical framework to investigate the spatiotemporal variations of LST and its responses to IS in Wuhan, China at both city scale and sub-region scale. The summer LST patterns in 2002–2017 are extracted by Multi-Task Gaussian Process (MTGP) model from raw 8-day synthesized MODerate-resolution Imaging Spectroradiometer (MODIS) LST data. At the city scale, the weighted center of LST (LSTWC) and impervious surface fraction (ISFWC), multi-temporal trajectories and coupling indicators are utilized to comprehensively examine the spatial and temporal dynamics of LST and IS within Wuhan. At the sub-region scale, urban heat island ratio index (URI), impervious surfaces contribution index (ISCI) and sprawl rate are introduced for further quantifying the relationships of LST and IS. The results reveal that IS and hot thermal landscapes expanded by 407.43 km2 and 255.82 km2 in Wuhan in 2002–2017 at city scale. The trajectories of LSTWCs and ISFWCs are visually coherent and both heading to southeast direction in general. At the sub-region scale, the specific cardinal directions with the highest ISCI variations are examined to be the exact directions of ISFWC trajectories in 2002–2017. The results reveal that the spatiotemporal variations of LST and IS are highly correlated at both city and sub-region scales within Wuhan, thus testifying the significance of steering IS expansion and renewal for controlling urban thermal environment deterioration.
Highlights
Unparalleled urbanization in China has led to the more obvious differences of temperature in urban relative to non-urban surroundings, a phenomenon known as the urban heat island (UHI)effect [1,2,3]
The cos α equals to −1 reveals that the angle between trajectories of LST Weighted Center (LSTWC) and Impervious Surface Fraction Weighted Center (ISFWC) at a specific time equals to 180◦, and cos α equals to 1 reveals that the angle equals to 0◦
The hot thermal landscapes of the study area have significantly expanded from 276.09 to 531.91 km2 and the impervious surfaces has expanded by 407.43 km2 at the city scale
Summary
Unparalleled urbanization in China has led to the more obvious differences of temperature in urban relative to non-urban surroundings, a phenomenon known as the urban heat island (UHI). Keeping in mind the importance of providing implications for steering urban expansion and intensification from the standpoint of LST and IS correlations at multiple scales either spatially or temporally, this study (1) generates typical summertime-scale LST patterns considering temporal variations of LST using non-parametric Multi-Task Gaussian Process (MTGP) model [32]; (2) quantifies the relationships between LST and IS by integrating moving trajectories and multiple indicators (e.g., spatial coupling indicators [41] and impervious surfaces contribution index (ISCI) [42]) at both the city scale and sub-region scale. The MTGP model are utilized to generate typical (1) at the city scale, characterizing the spatiotemporal variations of LST and IS patterns using. Scale, quantifying the coupling relationships of LST and IS in eight cardinal directions using ISCI [42], urban heat island ratio index (URI) [40] and sprawl rate [34,42]
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