森林冠层上湍流尺度、耗散率和湍流结构参数

Turbulence Length Scales,Dissipation Rates and Structure Parameters above the Forest Canopy

利用新型三维超声风速 温度仪 ,在中国东北长白山原始森林冠层以上观测的湍流资料 ,计算并分析了森林冠层上的湍涡特征长度尺度、湍流动量和热量耗散率、湍流动量和热量结构参数的特征。结果表明 :湍流动量湍涡特征长度尺度与稳定度参数Z L成正相关 ;湍流热量特征长度尺度与稳定度参数Z L在不稳定层结时 ,成正相关 ,在稳定层结时近似成负相关 ;在不稳定和稳定层结大气中 ,利用湍流谱方法和利用风速垂直分量方差、温度脉动方差和Richardson数计算的湍流动量、热量耗散率和湍流动量、热量结构参数有较好的一致性 ;无量纲湍流结构参数C2vz2 3 σ-2w和C2Tz2 3 σ-2T 是Richardson数的函数 ;湍流热力结构参数C2T 与感热通量w′T′具有较好的线性关系。

The turbulent data were measured using three-dimensional sonic anemometers/thermometers above a forest canopy,in the Changbai Mountains of northeast China.Turbulence length scales,dissipation rates and structure parameters above the forest canopy were calculated using the eddy correlation method.Results show that the turbulence characteristic length scales for momentum are negative interrelated with Z/L number;the turbulence characteristic length scales for heat is positive interrelated with %Z/L % number in unstable air and that is negative interrelated with %Z/L % number in stable air.The agreement between the momentum and heat dissipation rates calculated directly from the w spectrum(the turbulence spectral method)and indirectly from equations(15)(16)are quite good.The dimensionless turbulence structure functions C2 vz 2/3σ -2 w and C2 Tz 2/3σ -2 -T are functions of Richardson number in stable and unstable air.Turbulence structure parameters C2 T has a direct linear bearing on the sensible heat flux w′T′.