How to expand the cooling capacity of blue and green spaces in peri-urban areas throughout the entire diurnal cycle: Evidence from an inland multilake city

Blue and green spaces (BGs) play a critical role in mitigating the urban heat island effect, especially during heatwaves. However, limited research has been conducted on the impact of urban form factors on the cooling effect of BGs throughout the entire diurnal cycle. This study aimed to evaluate the cooling capacity of BGs in Wuhan, China, by considering the cooling distance (Delta Lmax) and cooling intensity (Delta Tmax) via the WRF-UCM model, considering the internal land use changes and spatial changes within the adjacent spaces of the BGs. The findings are as follows: 1) the BGs have a maximum Delta Tmax (1.44 degrees C) and Delta Lmax (2.15 km) during the daytime, which are reduced by 18.6 % and 85.4 %, respectively, at night; 2) during the daytime period, no green space within the BGs results in a greater Delta Tmax and Delta Lmax, while the law of diminishing marginal utility (LDMU) is disrupted by the disappearance of green spaces at night; and 3) open high-rise patterns show a larger Delta Tmax and Delta Lmax and lower Tmean in the daytime, with a smaller Delta Lmax and higher Tmean at night. The diurnal Tmean is consistently lower for the greening strategy. High-rise and low-density patterns can expand the BG cooling capacity, but they bring new heat waves at night.