Relationship between thermal inertia and urban heat sink in Beijing derived from Satellite images

During the monitoring of the UHI (urban heat island) effect using Advance Spaceborne Thermal Emission and Reflection Radiometer (ASTER) data, an urban heat sink was found. That means the surface temperature in the urban area is lower than that of the surrounding rural area. This paper focuses on the analysis of this urban heat sink developed in the winter morning of Beijing by thermal inertia because it is one of the typical subsurface thermal characteristics. Thermal inertia is a physical parameter representing the ability of a material to conduct and store heat, and in the context of planetary science, it is a measure of the subsurface´s ability to store heat during the day and reradiate it during the night. After getting the surface albedo and the land surface temperatures at day and night respectively, the thermal inertia was calculated using a real thermal inertia model. The result shows that the urban area has a bigger thermal inertia than that of the rural area. Which makes the materials in rural area have a rapidly increase in surface temperature than those in the urban area in winter morning which caused the formation of the urban heat sink.