北京地区城市化对辐射强迫的影响估算

能引起城市区域辐射强迫的因素较多,但是目前城市化引起的辐射强迫的相关研究较少.本文利用GLASS 反照率遥感数据和CERES地表短波辐射数据计算了近10年来北京地区城市化过程引起的辐射强迫,讨论了辐射强迫 的空间分布规律及数量统计特征.基于2000、2010年2期的Globeland30土地分类数据提取了城市边缘区,并结合辐射 强迫遥感数据计算了主城核心区、內缘区、各级外缘区的辐射强迫,探究了土地覆盖变化强迫因子、气候等其他强迫因子 的相对贡献大小.结果表明:近10年北京市全区域的辐射强迫为2.52 W·m-2,表现为增温效应,其中土地覆被不变区 域产生的辐射强迫为2.51W·m-2,耕地、林地是2种主要辐射强迫源;土地覆被变化区域产生的辐射强迫为2.67 W· m-2,非植被类型之间的土地覆被变化引起的平均辐射强迫为2.23W·m-2,有植被参与的土地覆被变化区域产生的辐 射强迫为2.95W·m-2;主城核心区的辐射强迫为-1.16W·m-2,表现为降温效应;辐射强迫变化与距离主城区的距离 呈先增大后减小的变化趋势.研究结果可为城市区域的辐射强迫研究提供参考,有助于了解北京市区域气候分布差异 

Influence of urbanization on radiative forcing in Beijing

Different forcing factors in urban areas contribute to the radiative forcing values.In the present work,GLASS albedo and CERES surface shortwave radiation data were used to calculate the surface radiative forcing due to changes in the surface albedo over the past 10 years in Beijing.Spatial distribution of radiative forcing and statistical characteristics were investigated.Urban fringe area was extracted from Globeland30 Land Use and Land Cover Change data.Combination with calculated radiative forcing of remote sensing data enabled extraction of radiative forcing values for urban district,inner zone and all levels in the outer edge region.Relationship between land cover change driving factors and climate-driving factors was explored.It has been found that over the past ten years,the radiative forcing in the whole of Beijing region was 2.52 W·m-2,leading to a temperature increase.The average value of radiative forcing in land cover-unchanged region was found to be 2.26 W·m-2,accounting for 89％ of all the radiative forcing in the whole region.Of such changes,cultivated land and woodland were the two major radiative forcing sources.The average value of radiative forcing in land-cover-changed region was found to be 0.26 W· m 2.The non-vegetation land cover change contributed 0.09 W·m-2,while vegetation-including-land-cover change generated radiative forcing of 0.18 W·m-2.In the city core area,radiation forcing was found to be-1.16 W·m-2,exhibiting as a cooling effect.The radiative forcing change was correlated to the distance away from urban district,first increasing and then decreasing from inside to outside.The present work provides a typical study of radiation forcing in urban areas,and data obtained would be helpful to understand differences in regional climate in Beijing.