| Urban heat island (UHI) effect was defined as the temperature difference between urban and rural area (Oke,1987). UHI is one of the hot topics in urban climate research, and also one of the environmental consequences of urbanization. UHI not only alters the local microclimate conditions in urban area, but also influences the physiological activities, phenology of plants and animals living in urban area, ecosystem functions, and health even life of urban habitants. UHI can deteriorate urban pollution, increase the energy consumption. Urban green space, an essential component of urban ecosystem, can markedly mitigate urban heat island effect. The effect of urban park on urban heat island has been well documented, but how urban park mitigates urban heat island at multi-scale has not been well addressed.In this thesis, methods of microclimate in situ observation, mobile observation, land surface temperature retrieval from remotely sensed imagery, and landscape pattern analysis were employed to study how urban park mitigate urban heat island effect in Shanghai, to quantitatively analyze how urban park (e.g. area, patch characteristics) and their structure affect urban thermal environment, to explore how the adjacent urban landscape pattern influence the cooling effect of urban park. My findings are as followed:(1) The temperature of urban park was clearly lower than that of the ambient environment in the autumn and winter. Urban Park, as cool island, could effectively mitigate of urban heat island effect.(2) The mitigation effect of urban park on UHI could be correlated to characteristics of park patch. Air temperature was negatively correlated to park area and fitted well with logarithmic function (R2=0.817, P<0.05). Air temperature was negatively correlated to park perimeter, and fitted well with power function (R2=0.7473, P<0.05). Air temperature was positively correlated to park shape index and well fitted with logarithmic function (R2=0.844, P<0.01). That is to say, the more complex the patch perimeter was, the higher the air temperature within the park would be. The land surface temperature was negatively correlated to park area, but no significance. But it was negatively correlated to park perimeter and could be fitted well with power function (R2=0.2792, P<0.01). Surface temperature difference between park and ambient environment could not be correlated to park patch characteristics.(3) The various plant community structure of the park showed different thermal effects on air temperature, land surface temperature and relative humidity. The effect of decreasing temperature and increasing humidity of all plant community was remarkable better than that of sealed surface. Arbor-grass and Arbor-shrub-grass type were better than grass type in regulating microclimate. The cooling effect of arbor-shrub-grass was higher than that of grass type by 1.71% in the day and 0.8% at night. Humidification effect of arbor-shrub-grass type was better than that of grass type by 8.95% during daytime and 2.34% during nighttime. The cooling effect of arbor-grass was higher than that of grass type by 5.93% during daytime and 0.18% during nighttime. Humidification effect of arbor-shrub-grass type was higher than that of grass type by 12.61% during daytime and 3.41% during nighttime. The cooling and humidification effect of compound community type was stronger in daytime than that at night. Cooling effect of grass was weaker in daytime than that at night. Grassland could increase relative humidity at night but decrease relative humidity in daytime.(4) The ambient temperature of the park could be correlated to landscape pattern but not be correlated to the distance to urban park. Temperature in commercial and residential areas with high-rise buildings was lower than that in residential area with low-rise buildings. The air temperature decreased sharply when park wind blew from high-rise to low-rise building area, but increased when from low-rise to high-rise building area.(5)The thermal effect of urban park varied with landscape pattern along urban-rural gradient which was affected by urbanization degree. Both air and surface temperature of parks in the area with higher urbanization were lower than that with lower urbanization. The mitigation effect of park on urban heat island increased with patch coverage of urban land use.
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