Research progress on the thermal environment of the urban surfaces

The dramatic changes in the thermal environment of urban surfaces could not only affect human health and wellbeing in terms of increased mortality and morbidity,but also alter components of the eco-environment,such as air and water quality,biodiversity,and net primary production. Over the last 50 years,within the context of rapid urbanization and human population density increases,ever-expanding impervious surfaces have triggered various environmental challenges in developing countries like China. Concerns related to environmental degradation,traffic jams,air pollution,and shortages of resources are expected to become more serious in conjunction with dramatic changes in the urban surface thermal environment. In light of this,studies on the urban surface thermal environment using quantitative research methods have become a hot topic for scientists in China,as well as worldwide. Hence,understanding the current progress in studies related to the urban surface thermal environment has importance and practical significance on the quantitative evaluation of the urban thermal environment and the promotion of sustainable urban development. In this paper,we first introduce the concepts of the urban surface thermal environment and urban heat island,main research methods,and data acquisition techniques. Secondly,we review the progress of research on the urban surface thermal environment considering the following aspects: the spatial temporal characteristics of the urban surface thermal environment and its changes,driving forces andmechanisms,urban surface radiation and energy balance,the relationship between urban surface heat islands and urban atmospheric heat islands and its evolution,urban greenbelt and water-body alleviation of the urban heat island effect,and scaling transformation of remote sensing temperature products. Finally, the difficulties, shortcomings, and existing bottlenecks in current research are discussed. Future research directions are equally proposed to provide a reference for future researchers interested in quantitative analysis of the urban surface thermal environment.