利用Landsat热红外数据研究1985年—2015年北京市冬季热场分布

由于北京城市中心区冬季供暖、汽车尾气、工业生产等因素的影响，以及冬季植被覆盖减少导致地表热惯量降低，致使北京市冬季地表热场与其他季节差异明显。冬季城市热场分布直接影响冬季大气颗粒物等污染物的扩散速度，因此，研究热场分布对了解城市热场在大气颗粒物污染中的贡献具有重要的意义。首先利用MODTRAN大气辐射传输模型计算大气透过率、大气上行辐射与大气下行辐射三个关键参数，通过构建查找表解算热红外波段辐射传输方程。使用数据模拟的手段评价了该方法的精度，结果表明，当比辐射率和水汽分别在±0.005和±0.6的误差范围内波动时，温度反演的误差分别小于0.348和2.117 K，表明该方法可达到较高的反演精度。选择长时间序列Landsat TM、ETM+数据，进行地表温度反演，得到1985年—2015年北京市的地表温度。基于反演的地表温度分析了北京市热场的时空分布。结果表明，北京冬季热场分布在空间上可分为四个层次：北京市二环内温度较高、二环到五环内低温环状特征明显、外围郊区温度高以及北京西部的山区温度最低;随着近30年来北京市的快速发展，热场分布在长时间序列中发生了明显的改变：随着北京城市的不断扩张，环状低温区域也不断扩大，从三环扩展到六环;城市二环以内热岛效应随时间推移而增强，且分布范围扩大。

Analysis of Thermal Field Distribution in Winter over Beij ing from 1985 to 2015 Using Landsat Thermal Data

Heat supply,automobile exhaust,industrial production and decrease of thermal inertia in winter caused by the decrease of vegetation coverage leads to an obvious difference in the distribution of the land ther-mal field in the winter compared with other seasons.The Urban thermal field distribution in the winter directly affects the spread of air pollutants,which has important implications for analyzing the contribution of the ther-mal field to particulate air pollution.Atmospheric transmissivity and atmospheric upwelling/downwelling radi-ance in simulations are first calculated using the moderate spectral resolution atmospheric transmittance algo-rithm and computer model (MODTRAN).Then,we solve the radiative transfer model of the thermal infrared band by constructing a look-up table.In addition,the accuracy estimation is performed using the simulated da-ta,showing that when the error range of emissivity and water vapor content are confined to ±0.005 and ± 0.6,respectively,the temperature retrieval error are less than 0.348 and 2.117 K,respectively indicating the high retrieval accuracy of the method.In addition,the long-term sequenced Landsat TM and ETM+ data were selected to retrieve land surface temperature (LST)during 1985-2015.The analysis of the temporal and spatial distribution of thermal fields in Beijing show that the spatial and temporal variations are observable.The spa-tial variation covers four levels:high temperature is distributed within the second ring,low temperature loops are distributed between the second and the fifth ring,high temperature is distributed in the outer suburb areas and the lowest temperature is distributed in the western mountainous areas.Meanwhile,the temporal variation of thermal field distribution changed a great deal during the rapid development in the past 3 decades:the low temperature loop expanded from the third to the sixth ring;the intensity and scope of the heat island effect within the second ring increased gradually.