Abstract
The urban heat island effect has always been one of the hottest issues in urban development. In this study, Landsat images from the summers of 2001, 2004, 2009, 2014 and 2018 were used to identify land cover type in six districts of Chongqing’s main city. Land cover was categorized as water, vegetation or impervious surface with the object-oriented method. Land surface temperature (LST) data was calculated with the atmospheric radiation transfer equation method, and was then divided into different heat island intensity grades. Next, the spatial and temporal changes in land cover type and heat island effect were analyzed in the six districts. Center migration analysis and heat island coefficients were used to quantitatively reflect the spatiotemporal evolution relationship between land cover and heat island effect. All six districts exhibited a trend of expanding impervious surface, with a 419.38% increase from 2001 to 2018, and shrinking vegetation, with a 17.81% decrease from 2001 to 2018. Also from 2001 to 2018, Yuzhong District had the most significant heat island effect, with a heat island coefficient 0.35 higher than the mean value of the whole study area. The impervious surface center migrated in different directions in each district. Both the direction and the corresponding velocity of the impervious surface and heat island centers were tightly correlated, with a correlation coefficient of 0.53. Relative heat island coefficients (the difference from the mean) of water ranged from −2.08 to −1.17 in different districts. That of impervious surface ranged from 1.60 to 1.93, and that of vegetation ranged from −0.22 to 1.09. The internal heterogeneity of land cover and heat island effect in Chongqing’s main city was huge. This study quantitatively analyzed the evolution of the heat island effect in the study area to help provide each district with some targeted suggestions for future urban planning.
Highlights
Urban environmental issues are at the intersection of three major problems in the world today: large population, limited resources and changing environment [1]
Based on Landsat images of six districts in the main city of Chongqing that were taken from 2001 to 2018, this study explored the spatial and temporal evolution of land cover and heat island effect, as well as the relationship between them throughout the study time frame
This study showed that the six districts experienced notable land cover changes from 2001 to 2018, with the general trend involving the expansion of impervious surface and the corresponding reduction of vegetation
Summary
Urban environmental issues are at the intersection of three major problems in the world today: large population, limited resources and changing environment [1]. One of the important areas of urban environmental research is the urban heat island effect, which refers to the special microclimate formed under the influence of climate and human activity [2,3,4]. The urban heat island effect is caused by the imbalance of the urban environment and has become a major public hazard, seriously affecting the normal lives and health of urban residents [5,6,7,8,9]. The first is to assess the impact of urban planning on the environment using urban models that focus on possible mechanisms and future scenarios [10,11].
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