Turbulence spectral structures and dissipation rates above and within the forest canopy

Three-dimensional velocity components and temperature were measured using t he new three-dimensional sonic anemometers/thermometers at two levels, abov e and within the forest canopy, in the Changbai Mountains of Northeast Chin a. Turbulence spectral structure, local isotropy property and dissipation r ates above and within the forest canopy were calculated using the eddy corr elation method. Results show that the normalized turbulent spectral curves have - 2/3 slopes in the inertial subrange. While the shapes of the spectra are in good agreement with the Kansas flat terrain results, the atmospheri c turbulence is anisotropic above the forest canopy. Within the forest cano py, the turbulence is approximately isotropic. Compared with measurements f rom previous studies over flat terrain, the velocity and temperature spectr a rates above and inside the forest canopy appear to shift toward higher fr equencies. The turbulent kinetic energy and heat energy dissipation rates a bove and inside the forest canopy are much larger than those obtained by Ka imal and Hugstrom over grassland and grazing land. The distinct features in the results of the present experiment may be attributed to the dynamic for cing caused by the rough surface of forest canopy.