Characteristics of an Urban Heat Island of Different Underlying Surfaces and the Assessment of a Human Comfort Index for Zhengzhou

The key factors of an urban heat island were monitored using a grid method to analyze seasonal and daily temperature changes. The difference in heat island intensity was investigated under the four micro environments, of: shed, no shed, beneath trees, and above vegetation. The graph of daily intensity changes plots as a hump-shaped curve, and the intensity at night shows as significantly higher than during daytime. The urban heat island intensity of the two vegetated micro environments was lower by 0.27°C compared with the site with no day shed. The urban heat island intensity in winter was approximately 2.5°C, and higher by 0.6°C in summer. Furthermore, the spatial distribution of the urban heat island intensity was closely related to surrounding industrial heat sources. The human comfort index in Renmin Park registered as the highest, because of its tree canopy. The ability to improve the microclimate is limited in Xiliu Lake Park, where the greening type is mainly lawn. However, the railway station square had a 16% frequency for a high human comfort index, perhaps owing to open space and good air flow.