土地利用变化下北京市热通量的时空演变

探究土地利用变化对城市热通量的影响，对城市用地规划和城市热岛缓解具有重要指导意义。利用混合像元组分排序对比和分层能量切割方法，通过Landsat系列数据反演的地表参数，结合气象再分析资料，估算了2004、2009、2014和2017年4期9月份的北京市地表瞬时热通量，依据同期的北京市土地利用图，分析了北京市热通量随土地利用变化的时空演变。结果表明：①北京市地表温度和热通量分布具有明显的空间异质性，山区和平原、平原不同土地利用类型之间差异明显；②在不同时期，土地利用类型间的地表温度和热通量的高低次序具有一致性，瞬时潜热通量，林地最高，为347.85~546.95 W/m²，其次为耕地、草地，建设用地最小，为225.23~349.03 W/m²，感热通量和地表温度则相反，建筑用地最高，分别为94.06~189.28 W/m²和25.18~32.25 ℃，耕地和草地次之，水体的最低，分别为28.15~102.55 W/m²和19.25~28.38 ℃；③土地利用类型转变引起的城市热通量变化方面，自然表面转为建设用地时，潜热通量急剧减少，感热通量增加，城区周边耕地的潜热通量受城市热辐射影响而增加，城市绿地能有效缓解城市热岛效应。

Temporal and Spatial Evolvement of Heat Flux in Beijing Under Land Use Change

Exploring the impact of land use change on urban heat flux has important significance for urban land use planning and urban heat island mitigation. Using the pixel component arranging comparing algorithm， four Beijing surface instantaneous heat fluxes in Septembers of 2004， 2009， 2014 and 2017 are estimated by the surface parameters retrieved from Landsat series data and meteorological reanalysis data， and the spatiotemporal variation of heat fluxes in Beijing is analyzed with the change of land uses during the same period. Results show： （1） the distribution of surface temperature and heat flux in Beijing has obvious spatial heterogeneity， and the difference between mountainous areas and plains and among different land use types in plains is obvious； （2） the order of surface temperatures or heat fluxes between different land use types has consistency at these four moments. For latent heat flux， the highest is 347.85~546.95 W/m² for forest land， followed by cultivated land and grassland， and the minimum is 225.23~349.03 W/m² for construction land. For sensible heat flux and surface temperature， the order is reversed， the highest for construction land is 94.06~189.28 W/m² and 25.18~32.25 ℃， followed by cultivated land and grassland， the lowest is 28.15~102.55 W/m² and 19.25~28.38 ℃ for water body； （3） in terms of change in urban heat fluxes caused by land use transformation， when natural surface is converted to construction land， latent heat flux is reduced and sensible heat flux increases. The latent heat flux of the arable land around the city is increased by the influence of urban heat radiation， and the urban green space can effectively alleviate urban heat island effect.