Synergistic cooling effects (SCEs) of urban green-blue spaces on local thermal environment: A case study in Chongqing, China

Both green and blue space are found to be effective for urban heat mitigation and air quality improvement. However, studies on the Synergistic Cooling Effects (SCEs) of green-blue spaces are limited. This paper aims to investigate the SCEs of green-blue spaces in Chongqing, a typical hot humid city in China, through the field measurement and numerical simulation. First, air temperature and relative humidity over different land-use sites (forest, lawn, and impervious pavement) were measured with and without water simultaneously, from July to August 2018. Experimental results revealed the SCEs of green-blue spaces were obvious in 7-12 m surrounding waterfront areas, where the mean air temperature reduction was 3.3 degrees C higher than the sums of cooling effect of standalone water and forest. Additionally, an ENVI-met model was validated against the measured data before conducting simulation for the study area in five scenarios, including one control group with no trees and four greening cases with different Leaf Area Index (LAI) values to investigate the importance of green infrastructure on the waterfront thermal environment. Simulation results showed that a decrease of 1.0 LAI can lead to a reduction of average air temperature by 0.19-0.31 degrees C, possibly owing to the enhanced ventilation flow.