A heated leaf replica technique for determination of leaf boundary layer conductance in the field
A heated leaf replica technique for determination of leaf boundary layer conductance in the field
复制标题
用于现场测定叶片边界层电导的加热叶片复制技术
DOI：
10.1016/0168-1923(94)02160-l
复制
发表时间：
1995
影响因子：
6.2
通讯作者：
P. Jarvis
中科院分区：
文献类型：
--
作者：
A. Brenner;P. Jarvis
本文提出了一种鲁棒场法，通过测量被电流加热的仿谷子叶片与作为参考的仿谷子叶片之间的温差，连续估计边界层电导。将风洞边界层电导的测量值与工程文献中公式计算的电导进行了比较。这两组值在低风速下是相似的。在风速大于2.5 m s−1时，模拟边界层的电导高于层流边界层的电导。分析了该方法的误差和假设。加热电流在复制品之间切换，以避免系统错误。利用该系统，在尼日尔一处防风林后的谷子作物田间测量了叶片边界层电导。分析了距离防风林4个距离和谷子种植季开始3个时期的风速(u)与边界层电导（ga）的关系。关系式ga= aub给出了参数a和b的一系列值，b的值在0.5 ~ 0.8之间，与气流的低频湍流度（由风速的标准差给出）呈线性关系。
This paper presents a robust field method for continuous estimation of boundary layer conductance by measurement of the temperature difference between a replica millet leaf which is heated with an electric current and an identical replica used as a reference. The measurements of boundary layer conductance in a wind tunnel were compared with conductances calculated using equations from an engineering text. The two sets of values are similar at low wind speeds. At wind speeds above 2.5 m s−1replica boundary layer conductances were higher than those calculated for a laminar boundary layer. Errors and assumptions of the technique were analysed. Heating current was switched between the replicas to avoid systematic errors. Using this system, leaf boundary layer conductance was measured in the field in Niger for a millet crop behind a windbreak. The relationship between wind speed (u) and boundary layer conductance (ga) was analysed for four distances from the windbreak and three periods at the start of the millet cropping season. The relationship ga= aubgave a series of values of parameters a and b. Values of b lay between 0.5 and 0.8 and were related linearly to the low frequency turbulence of the air flow (given by the standard deviation of the wind speed).