局地零平面位移对非均匀地表有效空气动力学参数的影响

Influence of local zero-plane displacement on effective aerodynamic parameters over heterogeneous terrain

利用最新提出的非均匀地表有效空气动力学参数联合计算方案,研究了三种非均匀地表情况下局地零平面位移对有效粗糙度和有效零平面位移影响的统计特征.结果表明,局地零平面位移对有效粗糙度有增幅作用,随着局地零平面位移的增加,有效粗糙度也相应增大,但局地零平面位移对有效粗糙度的增幅作用随地表粗糙变率增加而略有减小;有效零平面位移随局地零平面位移的增加而增加,但总小于线性加权平均值,且随着地表粗糙变率的增大,有效零平面位移却有所减小.

In this paper, we investigate the statistical features of the influences of local zero-plane displacement on effective roughness length and effective zero-plane displacement for three surface categories, with a so-called joint calculation scheme for effective aerodynamic parameters over heterogeneous terrain proposed by Zhong et al. [Zhong Z, Lu W, Song S and Zhang Y 2011 J. Hydrometeor. 12 1610]. The local zero-plane displacement is found to magnify the effective roughness length. However, such a magnification effect tends to decrease as the roughness step increases. On the other hand, the effective zero-plane displacement increases as local zero-plane displacement increasing, though it is always less than the area-weighted linear average of the local zero-plane displacement. However, the effective zero-plane displacement tends to decrease with the roughness step increasing.