西藏拉萨市热岛效应及其影响因子分析

采用2001年、2004年以及2007年三年的EOS/MODIS遥感信息反演的地面温度以及多年常规气象观测资料,讨论了拉萨市热岛现象及其可能影响因子。结果表明:(1)热岛强度的年、季节变化呈现逐渐增强的趋势,其中,冬季的热岛强度最强,其次是春季,秋季和夏季的热岛效应较弱;高温区基本位于城市中心或者县城所在地及其周围,低温区主要集中在各县的郊区;近年来拉萨地区的城市高温区域逐渐扩大,有些高温中心可能向某些区域偏移;遥感资料所获取的地表温度与平均气温之间存在一定的正相关性。(2)无论是年变化,还是季节变化,热岛强度都与风速呈正相关,与日照时数呈负相关,与蒸发量的相关在夏季和冬季分别呈正相关、负相关的相反状况;地表温度与植被分布具有较好的负相关关系,即在城区存在较高的地表温度分布和较小的NDVI,过渡到郊区具有温度减小、NDVI增加的特征;随着城市化进程的加剧,建筑面积不断扩大,人类活动明显增加,排放至大气的人为热增加,这些因素都可能导致热岛强度的增强。

Study on Urban Heat Island Effect and its Influencing Factors over Lhasa City

This paper present the urban heat island effect of Lhasa city and its possible influencing factors with land surface temperature (LST) of EOS/MODIS dataset and conventional observation. Results show that: (1) the heat island intensity is getting stronger both from annual and seasonal variation feature, especially in winter, spring secondly, and intensity is weak in autumn and summer. High temperature area is situated in the center of city and its surroundings and low temperature is located on the rural areas of different counties. The areas with high temperature expanded gradually and some centers may move to other places. LST has positive relationship with average temperature to some extent. (2) Whatever annual variation or seasonal variation, heat island intensity has positive (negative) relationship with wind speed (sunshine duration). And, it has positive (negative) relationship with evaporation in summer (winter). Furthermore, LST has good negative relationship with vegetation index, namely, there are higher LST and smaller NDVI in urban areas, but with lower temperature and greater NDVI in rural areas. Based on the intensified urbanization, the area of structure is extended continually, the increasing of human activity, more artificial heat in the atmosphere, all these above factors may cause the enhance of urban heat island intensity.