Abstract
In this study Yan’an City, a typical hilly valley city, was considered as the study area in order to explain the relationships between the surface urban heat island (SUHI) and land use/land cover (LULC) types, the landscape pattern metrics of LULC types and land surface temperature (LST) and remote sensing indexes were retrieved from Landsat data during 1990–2015, and to find factors contributed to the green space cool island intensity (GSCI) through field measurements of 34 green spaces. The results showed that during 1990–2015, because of local anthropogenic activities, SUHI was mainly located in lower vegetation cover areas. There was a significant suburban-urban gradient in the average LST, as well as its heterogeneity and fluctuations. Six landscape metrics comprising the fractal dimension index, percentage of landscape, aggregation index, division index, Shannon’s diversity index, and expansion intensity of the classified LST spatiotemporal changes were paralleled to LULC changes, especially for construction land, during the past 25 years. In the urban area, an index-based built-up index was the key positive factor for explaining LST increases, whereas the normalized difference vegetation index and modified normalized difference water index were crucial factors for explaining LST decreases during the study periods. In terms of the heat mitigation performance of green spaces, mixed forest was better than pure forest, and the urban forest configuration had positive effects on GSCI. The results of this study provide insights into the importance of species choice and the spatial design of green spaces for cooling the environment.
Highlights
It is well known that urbanization is one of the most powerful and visible anthropogenic forces onEarth [1,2,3]
The high temperature in 2015 was attributable to the strong global expansion intensity (EI) Nino climatic effect as well as severe local deforestation and construction activities due to construction of the new Yan’an city area, which caused dry and warm weather. These effects are readily discernible in the annual mean air temperature charts shown in Figure S2 showed the 20-min variations in the surface urban heat island (SUHI) intensity at 34 open impervious surface sites located close to the centre of Yan’an City in July
Our results showed that the four ground indexes were all significantly correlated with the mean land surface temperature (LST), i.e., a positive correlation with index-based built-up index (IBI) and negative correlations with FV, normalized difference vegetation index (NDVI) and modified normalized difference water index (MNDWI)
Summary
It is well known that urbanization is one of the most powerful and visible anthropogenic forces onEarth [1,2,3]. It is well known that urbanization is one of the most powerful and visible anthropogenic forces on. In China, cities are expanding rapidly as the economy grows, but land suitable for development is in short supply, in mountainous areas, where about one-fifth of the population lives. In the last decade, local governments have begun removing the tops of mountains to fill valleys and create land suitable for building. In cities such as Chongqing, Shiyan, Yichang, Lanzhou and Yan’an, tens of square kilometers of land have been created. In the Yan’an city area, the relatively warmer urban land surface/atmosphere
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