| Urban heat island (UHI) is a climate phenomena that urban air temperature significantly higher than the suburbs’, which caused by a variety of factors due to large-scale city gathering. Its existence has directly or indirectly negative influence on city dwellers’life and health. Urban green space is a significant component in the urban ecosystem, which can effectively decline the heat island effect. With the intensification of urbanization, the urban heat island effect has been increasingly become one of the salien characterization of urban climate, more and more attention has been paid from scholars at home and abroad. As the upper reaches of Yangtze River region’s economic, scientific and technological center and transportation hub, the the degree of urbanization is getting higher and highe in Chongqing. The size of the city is increasing, as well as the population, the urban heat island effects therefore become more noticeable.This paper studied the present distribution of heat island of main urban area (2011) and spatial and temporal evolution patterns in recent five years (2007-2011) using the data collected by weather stations, Landsat4-5TM image data, microclimate observation data and the integrated application of the3S technology. In addition, based on the different scale from urban green space, residential green space to landscape patches, in order to make clear that the role of urban green space abatement effect on urban heat island, and quantitative analysis of characteristics of urban green space and its internal thermal environment effect. This study had the following conclusions:(1) The temperature in main urban area was significantly higher than that in the suburbs at the same time period. The heat island distributions in main urban area were point, line and face patterns. In recent five years, the spatial evolution of urban heat island showed that strong and secondly strong urban heat island changed from dominating in the south to north and south distributing balanced. Overall, the area and scope of urban heat island were gradually increasing.(2) The temperature abatement effect of urban green space was correlated to the plant coverage of green patches. The temperature abatement degree had a positive relationship with patch area and its perimeter, while negatively related to the shape of green patches. Except for the green space of cross-bridge, temperature abatement degree of green space positively correlated to NDVI value. Park green space NDVI value was positively correlated to its temperature abatement degree (P<0.01), but not for the green space shape index (P>0.05). The perimeter and area of community green space significantly correlated to those temperature abatement degree (P<0.05), but not for the NDVI value (P>0.05). However, the area, perimeter and shape index of cross-bridge green space positively correlated to the temperature abatement degree (P<0.01). The perimeter and NDVI value of road green space were positively correlated to the temperature abatement degree (P<0.05), but not for the area and shape index of road green space.(3) The temperature abatement effect in residential green space did not change significantly in a single day. The temperature abatement degree of the tree+shrub+grass mode and tree+grass mode initially increased and then declined with the maximum value at the12:00and13:00. The temperature abatement effect of different plant allocation mode was different. The order was as followings:tree+shrub+grass> tree+shrub> tree+grass> shrub> grass. Small discrepancy of temperature abatement effect existed between the tree+shrub+grass, tree+shrub and tree+grass mode. Generally, the temperature abatement degree of green space dominated by tree significantly stronger than that of in shrub and grass. The temperature abatement degree of green space differentiate from the green space percentage, volume rate and architectural patterns, and the different rank was as following:Junyi new world>Luneng new city>Shuijin city. |
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