Effect of Land Cover Fractions on Changes in Surface Urban Heat Islands Using Landsat Time-Series Images.

Tao Chen,Anchang Sun,Ruiqing Niu

doi:10.3390/ijerph16060971

Abstract

Man-made materials now cover a dominant proportion of urban areas, and such conditions not only change the absorption of solar radiation, but also the allocation of the solar radiation and cause the surface urban heat island effect, which is considered a serious problem associated with the deterioration of urban environments. Although numerous studies have been performed on surface urban heat islands, only a few have focused on the effect of land cover changes on surface urban heat islands over a long time period. Using six Landsat image scenes of the Metropolitan Development Area of Wuhan, our experiment (1) applied a mapping method for normalized land surface temperatures with three land cover fractions, which were impervious surfaces, non-chlorophyllous vegetation and soil and vegetation fractions, and (2) performed a fitting analysis of fierce change areas in the surface urban heat island intensity based on a time trajectory. Thematic thermal maps were drawn to analyze the distribution of and variations in the surface urban heat island in the study area. A Multiple Endmember Spectral Mixture Analysis was used to extract the land cover fraction information. Then, six ternary triangle contour graphics were drawn based on the land surface temperature and land cover fraction information. A time trajectory was created to summarize the changing characteristics of the surface urban heat island intensity. A fitting analysis was conducted for areas showing fierce changes in the urban heat intensity. Our results revealed that impervious surfaces had the largest impacts on surface urban heat island intensity, followed by the non-chlorophyllous vegetation and soil fraction. Moreover, the results indicated that the vegetation fraction can alleviate the occurrence of surface urban heat islands. These results reveal the impact of the land cover fractions on surface urban heat islands. Urban expansion generates impervious artificial objects that replace pervious natural objects, which causes an increase in land surface temperature and results in a surface urban heat island.

Highlights

IntroductionThe process of urbanization transforms the natural landscape for anthropogenic urban land uses, which leads to changes in the physical characteristics of the surface of the transformed areas [1]
The process of urbanization transforms the natural landscape for anthropogenic urban land uses, which leads to changes in the physical characteristics of the surface of the transformed areas [1].Urbanization is likely to cause both significant changes in land use and land cover and severe environmental deterioration
We explored the connection between the surface urban heat island (SUHI) and land cover fraction (LCF) in the Metropolitan Development Area of Wuhan by using six Landsat images acquired in September and October during the period of 1990 to 2014

Summary

Introduction

The process of urbanization transforms the natural landscape for anthropogenic urban land uses, which leads to changes in the physical characteristics of the surface of the transformed areas [1]. Urbanization is likely to cause both significant changes in land use and land cover and severe environmental deterioration. One of the environmental consequences of urbanization is the surface urban heat island (SUHI) effect. The SUHI effect was first proposed by Howard, who found relatively higher temperatures in urban areas than in the surrounding suburban/rural areas [2]. The SUHI effect reduces human comfort and is harmful to urban residents [3,4].

Methods

Results

Discussion

Conclusion