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The Characteristics and Parameterization of Aerodynamic Roughness Length over Heterogeneous Surfaces
LU Li,LIU Shaomin,XU Ziwei,YANG Kun,CAI Xuhui,JIA Li,WANG Jiemin
State key Laboratory of Remote Sensing Science, School of Geography, Beijing Normal University, Beijing 100875; Meteorological Information Center of Beijing, Beijing Meteorological Bureau, Beijing 100089;State key Laboratory of Remote Sensing Science, School of Geography, Beijing Normal University, Beijing 100875;State key Laboratory of Remote Sensing Science, School of Geography, Beijing Normal University, Beijing 100875;Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing 100085;Department of Environment Science, Peking University, Beijing 100871;Alterra Green World Research Institute, Wageningen University and Research Centre, Wageningen, The Netherlands;Cold and Arid Regions Environment and Engineering Research Institute, Chinese Academy of Sciences, Lanzhou 730000
Abstract Aerodynamic roughness length (z0m is a key factor in surface flux estimations with remote sensing algorithms and/or land surface models. This paper calculates z0m over several land surfaces, with 3 years of experimental data from Xiaotangshan. The results show that z0m is direction-dependent, mainly due to the heterogeneity of the size and spatial distribution of the roughness elements inside the source area along different wind directions. Furthermore, a heuristic parameterization of the aerodynamic roughness length for heterogeneous surfaces is proposed. Individual z0m over each surface component (patch) is calculated firstly with the characteristic parameters of the roughness elements (vegetation height, leaf area index, etc.), then z0m over the whole experimental field is aggregated, using the footprint weighting method.
