The contrasting trend of global urbanization-induced impacts on day and night land surface temperature from a time-series perspective

Increasing impervious surface area (ISA) is a major contributor to the rising land surface temperature (LST). Understanding the warming effect of ISA quantitively is crucial to alleviate the urban heat island effect. However, the quantitative analyses of urbanization-induced LST change globally remain to be determined over past decades. Here, we first characterized the response of LST to ISA (i.e., δLST) in 369 global cities using Terra MODIS LST product (1km) and the global artificial impervious area dataset (30m). We then investigated the spatiotemporal changes of δLST and its associated driving factors, including enhanced vegetation index (1km), albedo (500m), population (100m), air temperature (0.1°), and precipitation (0.1°). The analysis was conducted using linear regression models from 2000 to 2010 at the pixel level. The results illustrate that (1) the δLST in urban areas shows a negative trend during daytime (–0.2971°C/% and –0.0870°C/%) and a negative trend at night (0.0938°C/% and 0.0048°C/%) in arid and temperate regions, respectively. While in tropical regions, the δLST remains positive throughout the day, but it exhibits an opposite trend in snow regions. (2) The magnitude of nighttime δLST is stronger compared to daytime globally, which is more significant in arid regions with the largest ΔδLST values (i.e., diurnal variations) in urban (0.3909°C/%) and rural (0.3262°C/%) areas. Besides, the impervious surface has a distinct impact on LST in summer and winter, particularly at night. (3) In temperate regions, δALB (negative) and δAT (positive) are dominant factors in regulating δLST during daytime and nighttime. However, in arid regions, the daytime and nighttime δLSTs are negatively correlated by urban population and vegetation, respectively. These findings provide a quantitative understanding on long-term LST variations and driving factors behind at the pixel level, suggesting that urban greening and increasing surface albedo are effective strategies to mitigate the urbanization-induced surface warming.