Observational Study of Atmospheric Turbulence above and within a Pine Forest

Two three-dimensional sonic thermo-anemometer probes were used to measure velocities and temperatures above and within a pine forest near Chongqing city,Sichuan Province, in order to comprehend mass and energy exchange between atmosphere and forest. The turbulent fluxes of momentum and heat, and statistics and spectra of wind speed fluctuations were calculated from the digital data sampled at rate of both 1s~(-1) and 11s~(-1) , using eddy correlation and FFT method. The results show that above the canopy kinetic momentum was transported downwards, while within the canopy it was transported upwards. Within the canopy mean skewness of u was positive and that of w negative. Above the canopy both the dimensionless standard deviation of u and w and dimensionless turbulence, dissipation rate were functions of local Monin-Obukhov length, while within the canopy those variables did not show the correlations. The "—2/3" power rules, however, were existed at the inertial subrange of power spectra of wind speed either above the canopy or within it.

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