The footprint of urban areas on global climate as characterized by MODIS
The footprint of urban areas on global climate as characterized by MODIS
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DOI：
10.1175/jcli3334.1
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发表时间：
2005-05-15
影响因子：
4.9
通讯作者：
Zhang, DL
中科院分区：
文献类型：
--
作者：
Jin, ML;Dickinson, RE;Zhang, DL
气候变化的一个机制是土地覆盖或土地利用变化的综合影响。这种变化在城市地区尤其显著，因为世界上有许多人口居住在城市地区。卫星观测为确定城市化造成的物理变化的特征提供了基础。特别是，美国国家航空航天局（NASA）Terra卫星上的中分辨率成像光谱仪（MODIS）测量表面光谱反射率、热发射率和辐射温度。更好地理解这些测量应该提高我们对城市化气候影响的认识，以及我们确定气候模型计算城市化影响所需参数的能力。为此目的，将城市地区与邻近的非城市表面的辐射表面温度、发射率和反射率进行对比是有用的。在这些属性中，地表温度已被最广泛的研究以前的背景下，“城市热岛”（UHI）。然而，除了少数详细的研究，城市热岛主要是在地面空气temperature.To提供一个全球性的分析，这些属性的纬向平均值在这里测量的城市地区与邻近的非城市地区。此外，个别城市进行了检查，以说明这些变量的变化与土地覆盖在不同的气候条件下[例如，在北京、纽约和凤凰城（美国的一个沙漠城市）。卫星测得的表面温度与地表气温有关，但不一定具有相同的季节和日变化，因为它们更多地与地表能量交换过程相关联，而较少地与上覆大气柱相关联。因此，从皮肤温度的城市热岛效应被证明是明显的，在白天和夜间，而不是在夜间，如先前建议从地面空气温度测量。此外，城市地区的特点是夏季的植被覆盖率远低于农田和落叶林，但冬季与森林相似。因此，城市表面可以区分从非城市表面，通过使用一个建议的指数由皮肤温度乘以温度。
One mechanism for climate change is the collected impact of changes in land cover or land use. Such changes are especially significant in urban areas where much of the world's population lives. Satellite observations provide a basis for characterizing the physical modifications that result from urbanization. In particular, the Moderate Resolution Imaging Spectroradiometer (MODIS) instrument on the National Aeronautics and Space Administration (NASA) Terra satellite measures surface spectral albedos, thermal emissivities, and radiative temperatures. A better understanding of these measurements should improve our knowledge of the climate impact of urbanization as well as our ability to specify the parameters needed by climate models to compute the impacts of urbanization. For this purpose, it is useful to contrast urban areas with neighboring nonurban surfaces with regard to their radiative surface temperatures, emissivities, and albedos. Among these properties, surface temperatures have been most extensively studied previously in the context of the "urban heat island" (UHI). Nevertheless, except for a few detailed studies, the UHI has mostly been characterized in terms of surface air temperatures.To provide a global analysis, the zonal average of these properties are presented here measured over urban areas versus neighboring nonurban areas. Furthermore, individual cities are examined to illustrate the variations of these variables with land cover under different climate conditions [e.g., in Beijing, New York, and Phoenix (a desert city of the United States)]. Satellite-measured skin temperatures are related to the surface air temperatures but do not necessarily have the same seasonal and diurnal variations, since they are more coupled to surface energy exchange processes and less to the overlying atmospheric column. Consequently, the UHI effects from skin temperature are shown to be pronounced at both daytime and nighttime, rather than at night as previously suggested from surface air temperature measurements. In addition, urban areas are characterized by albedos much lower than those of croplands and deciduous forests in summer but similar to those of forests in winter. Thus, urban surfaces can be distinguished from nonurban surfaces through use of a proposed index formed by multiplying skin temperature by albedo.