The turning point between urban vegetation and artificial surfaces for their competitive effect on land surface temperature

Abstract

Abstract As the two most common types of land cover in cities, vegetation (Veg) and artificial surfaces (AS) often exhibit competitive effects, i.e., cooling effect and warming effect, on land surface temperature (LST). Hitherto, the change of this competitive effect along the proportion gradient of AS within urban areas and their implications for urban construction still lacks adequate attention and discussion. To fill this gap, we made a quantitative analysis of the relationship between Veg (trees or grassland), AS and LST in 35 major cities of China by using Ziyuan-3 (ZY-3) high-resolution satellite observations. Results found that: (1) in each city, there exists a certain threshold (or “turning point”) along the proportion gradient of AS, exceeds which AS replaces Veg as the variable that have dominant effect on LST (i.e., the warming effect of AS is always stronger than the cooling effect of Veg); (2) for most cities, the turning points of AS for grassland and trees are 60% and 70%, respectively; (3) the turning point for cities at a higher development level is lower, indicating that even a relatively low AS coverage (∼50–60%) in these areas can lead to an evident rise in LST; 4) compared to cities in temperate and tropical climate zones, the turning point for arid/semi-arid cities is higher, implying that their urban Veg shows a better performance in mitigating urban heat stress. This study represents a systematic investigation of the competitive effect of urban Veg and AS on LST, and the understanding of turning point provides a new perspective for stakeholders to integrate urban development and temperature regulation in planning initiatives.