Turbulence Statistics within and above a Pine Forest
Date Issued
2004
Date
2004
Author(s)
Huang, Li-Chung
DOI
zh-TW
Abstract
This study investigates the canopy turbulence structure. Three-dimensional velocities and temperature were measured within and just above a pine forest. Vertical profiles of horizontal velocity, sensible heat flux, momentum stress, standard deviation, skewness coefficient, kurtosis coefficient and correlation coefficient are calculated for different thermal stabilitity conditions. In this study, the thermal stability is depends on the local heat flux profile instead of the thermal stability coefficient, usually used in the surface layer. Furthermore, this study analyzes the structure of canopy turbulence by quadrant analysis, ramps analysis, autocorrelation, crosscorrelation, and shannon entropy. The purpose of this study is to understand the structure of the canopy turbulence under different thermal stabilities, and aims at a parameterization framework of turbulent statistics for implementation in the Lagrangian stochastics models.
The most important results include: 1) the turbulence characteristics of longitudinal velocity for the upper canopy and the lower canopy are different; 2) Gaussian entropy deficit is more efficient in identifying the Gaussian turbulence than the higher-order statistics; 3) thermal stability did not play an important role in lower-order velocities statistics but influence obviously on the statistics of the higher-order velocities and all temperature; 4) the eddy size is increased with decreasing the heat flux.
Subjects
森林植被
紊流結構
紊流統計
相干性渦旋
自關聯性
象限分析
熱穩定度
渦旋大小
相關聯性
熵
statistics
Canopy turbulence
Thermal stability
Type
thesis
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