Experimental Studies of Turbulence in the Surface Layer: Phase II

这项研究的目的是系统地评估大气近地面层湍流动能的源和汇。稳定性对湍流能量方程的归一化项(所谓的“Phi函数”)的影响正在一系列相对较小的现场实验中进行研究。由于相互矛盾的后续实验结果和对稳定性影响的未完成调查，这些函数的特殊形式和关系中的经验常数目前仍不确定，这些函数通常用于参数化下边界层。本实验将测量风廓线、湍流谱、地面热能平衡和鲍文比，以评估适度偏离中性对(1)风切变和浮力产生湍流的速率，(2)湍流耗散率，(3)局部获得或损失能量的净速率的散度项总和的影响。为了获得这一预算数据，将增加额外的测量：混合层的深度将被声学监测，湍流能量的垂直湍流通量将通过涡旋相关分两级测量。所有田间试验将在粗糙度均匀的大范围裁剪表面上进行。弗伦岑教授完全有资格进行这些测量；他在以前的现场测量中拥有相当多的经验，特别是在使用他独特的低惯性风速计方面。

The object of this research is a systematic evaluation of sources and sinks of turbulent kinetic energy in the atmospheric surface layer. Effects of stability on the normalized terms of the turbulent energy equation (the so-called "phi functions") are being investigated in a graduated series of comparatively small field experiments. The particular forms of and the empirical constants in relations for these functions now commonly used to parameterize the lower boundary layer remain uncertain because of contradictory results of subsequent experiments and incomplete investigation of the effects of stability. This experiment will measure wind profiles, turbulence spectra, surface thermal energy balances, and Bowen ratios in order to evaluate the effects of moderate departures from neutrality upon (1) the rates at which turbulence is produced by wind shear and buoyancy, (2) the turbulence dissipation rate, (3) the net rate at which energy is locally gained or lost by the sum of the divergence terms. To obtain this budget data, additional measurements will be added: the depth of the mixed layer will be monitored acoustically and the vertical turbulent flux of turbulent energy will be measured by two levels by eddy correlation. All field experiments will be conducted over extensive cropped surfaces of uniform roughness. Professor Frenzen is well qualified to make these measurements; he has considerable experience in previous field measurements especially in the use of his unique low-inertia anemometers.