Turbulence anisotropy in complex terrain compared to open terrain

Although small scale turbulent motion is isotropic or nearly so, larger scale motion in the atmosphere is known to be anisotropic at the scales of maximum turbulence kinetic energy and significant momentum transfer. Over open terrain (CASES99 main tower data), the anisotropy of different scales of turbulence follows a predictable pattern for neutral, shear dominated, flow. The same pattern of anisotropy is expected for flow over complex terrain in cases where the shear structure is similar to the shear found over open terrain. Mountain terrain creates the possibility of frequent cases of complex shear structure. Multiresolution decomposition of the data is used to separate the turbulence into different scales of motion, and Reynolds stress tensor analysis is used to determine the anisotropy characteristics.