摘要
城市下垫面非均匀性度量研究对于改进中尺度数值模式、提高城市气象预报准确率具有重要意义.基于分形布朗运动理论和Landsat-TM卫星遥感图像,估算了2011年北京典型下垫面类型个例和整个空间区域的分数维,由此来度量北京城市下垫面的非均匀性特征.研究结果显示:分数维能有效度量北京城市下垫面的非均匀程度,典型下垫面类型的分数维高低顺序为商业区>大型居民区>城市绿地>农田>林地>水体;北京六环内区域及郊区城镇地表非均匀特征明显,分数维一般在2.50以上,北京城市中心(二环内)存在一个分数维相对低值区,二环—四环之间区域分数维普遍较高,在2.70以上,五环以外分数维则不断降低,反映出北京城市下垫面非均匀性从中心向外呈低—高—低的空间分布;下垫面类型中建筑用地、绿地、未利用地、农田、林地和水体的平均分数维分别为2.71、2.62、2.55、2.38、2.30和2.28,分数维值的高低反映了城市下垫面类型的非均匀程度大小,对定量描述城市边界层参数的复杂特征具有参考意义.
Measure of the heterogeneity of urban underlying surface is important to improve meso-scale numerical model and increase accuracy of urban weather forecast. Based on fractional Brownian motion theory and Landsat-TM satellite images,fractal dimensions of Beijing＇s typical underlying surface types and the entire urban region are estimated for 2011,which is used to measure the heterogeneity of Beijing＇s underlying surface structure. The results indicate that the fractal dimension can effectively measure the heterogeneity characteristics of Beijing＇s surface. The heterogeneity values for different typical ground object samples are ranked in descending order as business district,residential district,green field,crop,woodland,and water body. The regions inside 6th-ring road and suburban towns have significant heterogeneity,with fractional dimensions generally higher than 2. 50. There is a low fractional dimension region in Beijing＇s center area within 2nd-ring road region. Fractional dimension of region between 2nd-ring road and 4th-ring road is highest and above 2. 70,and it decreases outside of 5th-ring road. In a whole,the heterogeneity of urban underlying surface is distributed as firstly increase then decrease from city center to surrounding areas in Beijing. The exurb crop and woodland have low heterogeneity. For different underlying surface types,average fractional dimension of building,green land,unutilized land,crop,forest and water are 2. 71,2. 62,2. 55,2. 38,2. 30 and 2. 28,respectively. And the values of fractal dimensions show the quantitative measure of heterogeneity of various underlying surface types,which bears reference for quantitative description of complexities of urban boundary layer.
出处
《南京信息工程大学学报（自然科学版）》
CAS
2015年第5期444-450,共7页
Journal of Nanjing University of Information Science & Technology（Natural Science Edition）
基金
国家自然科学基金(41175015)
城市气象科学基金(IUMKY&UMRF201102)
北京市气象局"城市边界层观测分析与精细模式"创新团队
关键词
城市下垫面
非均匀
分形布朗运动
分数维
北京
urban underlying surface
heterogeneity
fractional Brownian motion
fractal dimension
Beijing
