基于Landsat TM/ETM+的天津城区及滨海新区热岛效应时空变化研究

利用1987年、1998年、2004年和2008年4景Landsat TM/ETM+数据的热红外波段数据反演天津市地表亮温,并对绝对亮温值进行归一化处理得到相对亮温。通过对相对亮温分布图进行时空分析可知,自1987年到2008年,天津市热岛效应主要发生在中心城区、滨海新区以及道路沿线等区域。热岛范围在加大,强度也在增加。中心城区热岛效应不断加剧,滨海新区的热岛效应则从无到有,从弱到强,变化十分明显。并分析了热岛现象产生和异常的原因,有降水变化、农作物收割、公路建设和建成区增加。

Study of Temporal and Spatial Variation of Urban Heat Island Based on Landsat TM in Central City and Binhai New Area of Tianjin

This paper studies UHI(Urban Heat Island) spatial and temporal changes in central city and Binhai New Area in Tianjin with Landsat TM/ETM+. 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 city. Several methods can be used to retrieve from TM/ETM+, such as light temperature, single-channel algorithm and mono-window algorithm. This paper retrieved land surface light temperature (LSLT) of Tianjin from Landsat TM thermal band data from four dates in 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 is 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 is also becoming larger and harder. The effect of UHI in central city is aggravated and then decreased. 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 shows that there are two abnormal high temperature areas in Dagang Reservoir and southwest of Tianjin. The reason for the former abnormal area is 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 in mature 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.