Study on temporal and spatial variation of the urban heat island based on Landsat TM/ETM+ in central city and Binhai New Area of Tianjin

Thermal band data from TM/ETM+ has higher spatial and temporal revolution. As a result it can be used in UHI studies of small research areas, such as a city. Several methods can be used to retrieve from TM/ETM+, such as light temperature, single-channel algorithm and mono-window algorithm. UHI(UrbanHeat Island) spatial and temporal changes in central city and Binhai New Area of Tianjin were carefully studied based on Landsat TM/ETM+. Land surface light temperature (LSLT) of Tianjin was retrieved from Landsat TM thermal band data from four data of the year 1987, 1998, 2004 and 2008. In order to avoid errors resulting from different seasons, absolute LSLT is transferred to comparative LSLT by means of normalizing. And then the comparative LSLT was classified into distribution maps. The proportion of temperature class was also calculated and plotted. The result of analysis of maps and plots shows that UHI mainly occurred in central city, Binhai New Area, and areas along the roads between two areas. From 1987 to 2008, UHI was also becoming larger and harder. The effect of UHI in central city was aggravating and then decreasing. The effect of UHI in Binhai New Area started from scrath, from less to more, and experienced obvious changes. Especially effect of UHI in Dagang District started from scrath, from less to more and then kept constant. The distribution map of 1987 showed that there were two abnormal high temperature areas in Beidagang Reservoir and in the southwest of Tianjin. The reason for the former abnormal area was precipitation deficit in the period between spring and summer. The reason for the latter is the naked land due to harvest of wheat and low content of chlorophyll immature crops. Since 1998, there has been a strip of high temperature area, which was caused by extending built-up areas along the roads between central city and Binhai New Area. Finally, one of the reasons for UHI temporal changes in both central city and Binhai New Area is built-up area increasing.