基于卫星数据与GIS技术的北京地区粗糙度长度估算研究

Estimation of Roughness Length of Beijing Area based on Satellite Data and GIS Technique

基于卫星数据与GIS技术,利用形态学模型,建立了以植被类型、冠层叶面积指数和植被高度为主要输入参数的植被粗糙度长度Z0估算模型和以建筑物覆盖率和建筑物高度为主要输入参数的城市Z0估算模型;并以北京地区为例,分别利用2012年MODIS（中分辨率成像光谱仪）卫星资料和2005年GLAS（地球科学激光测高系统）卫星资料估算得到1 km空间分辨率北京主要植被地区Z0,利用2009年1∶2000北京城市基础地理信息和GIS技术估算得到北京城市地区100 m空间分辨率的Z0,并利用植被相关研究结果与北京城市地区大气所铁塔（高325 m）研究结果进行了比较和验证分析。结果表明,2012年北京主要植被地区Z0为0～1.3 m,存在着明显的季节变化,山区森林的Z0一般为0.6～1.3 m,冬季高于夏季;平原农田的Z0一般为0～0.4 m,夏季高于冬季。北京城市地区Z0存在明显的空间变化,一般为0.1～8.0 m,显示北京城市下垫面的高度非均匀特征;其中Z0值在1.0 m以上的地区主要分布于北京四环区域内及四环外大型居民社区、经济开发区和郊区县城中心,在二环区域内存在一个Z0低值区,大部分Z0在0.5 m以下;大气所铁塔周围Z0值为4.0～9.0 m,与采用气象学方法的研究结果具有较好一致性。比较和验证分析显示本文Z0估算方法较为合理可信,表明在区域范围内,遥感和GIS技术是未来估算区域尺度复杂下垫面空气动力学参数的一种有效途径。

A method is established in this paper for estimating aerodynamic roughness length Z0 for vegetation region and urban area on regional scale. Based on satellite data and GIS techniques and morphological model,three key parameters,vegetation types,canopy leaf area index（LAI）and plant height,are taken as inputs to estimate the Z0 for vegetation region. And buildings density and height are involved to calculate the Z0 for urban area. With the proposed model,the Z0 of vegetation region with resolution 1 km are estimated firstly. Here the vegetation canopy LAIs are derived from Moderate-Resolution Imaging Spectro radiometer（MODIS）satellite data in2012. The height of forest is estimated with Geoscience Laser Altimeter System（GLAS）satellite data in 2005.And the height of crop is phonological constant. Then the Z0 with resolution 100 m within urban region is estimated with 1∶2000 basic geographical data. To validate the results the existing similar researches are involved into comparing and analysis. The results showthat in 2012 the Z0 is 0 ～ 1. 3 m in vegetation region,and the generalized roughness length Z0/Zhis 0. 01 ～ 0. 13,which varies distinctly according to the seasons. Generally,the Z0 is 0. 6 ～ 1. 3 m in mountainous forests,and Z0/Zh0. 06 ～ 0. 10,which is higher in winter than in summer. While for the farmland in plain region,the Z0 is 0 ～ 0. 4 m,and Z0/Zh0. 01 ～ 0. 13,higher in summer than in winter.For Z0 in urban area,generally 0. 1 ～ 8. 0 m,there exists obvious spatial variation which demonstrate the strong heterogeneity of the surface. The regions with Z0 higher than 1.0 m include area inside the forth- ring,and the large residential community,economic development zone outside the forth-ring,and country center in suburbs.Inside the second-ring region,there is a zone with lowvalues,lower than 0. 5 m. The estimated Z0 value around the atmospheric tower,a typical urban scientific experiment plot with 325 m high in Beijing urban area,is 4. 0 ～9. 0 m,which is consistent with the results based on metrological methods. Our results have demonstrated the proposed method is reasonable and credible in the study area,which also indicates that remote sensing and GIS technology is a valid approach to estimate aerodynamic parameters of complicated underlying surface at regional scale.