Summertime heat island intensities in three high-rise housing quarters in inner-city Shanghai China: Building layout, density and greenery

Abstract

Shanghai as the largest city in China has been suffering from the ever-worsening thermal environment due to the explosive urbanization rate. As an indication of urbanization impact, urban heat islands (UHI) can give rise to a variety of problems. This paper reports the results of an empirical study on the summertime UHI patterns in three high-rise residential quarters in the inner-city Shanghai. Site-means of UHI intensity are compared; case studies are carried out on strategically located measurement points; and regression analysis is followed to examine the significance of the on-site design variables in relation to UHI intensity. It is found that site characteristics in plot layout, density and greenery have different impacts on UHI-day and UHI-night patterns. Day-time UHI is closely related to site shading factor. Total site factor (TSF) as an integrated measure on solar admittance shows a higher explanatory power in UHI-day than sky view factor (SVF) does under a partially cloudy sky condition. Night-time UHI cannot be statistically well explained by the on-site variables in use, indicating influences from anthropogenic heat and other sources. Evaporative cooling by vegetation plays a more important role at night than it does at day. Considered diurnally, the semi-enclosed plot layout with a fairly high density and tree cover has the best outdoor thermal condition. Design implication based on the findings, with consideration on other important environmental design issues, is briefly discussed.