Is the empirical coefficient b for the relaxed eddy accumulation method constant?
Is the empirical coefficient b for the relaxed eddy accumulation method constant?
复制标题
松弛涡累积法的经验系数 b 是常数吗？
DOI：
10.1007/s10874-014-9282-0
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发表时间：
2014
期刊：
影响因子：
--
通讯作者：
Hirata R.
中科院分区：
文献类型：
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作者：
Sakebe A;Ueyama M;Kosugi Y;Hamotani K;Hirano T;Hirata R.
松弛涡累积 (REA) 方法是测量痕量气体通量的涡流协方差方法的一种有吸引力的替代方法，因为它允许使用具有最佳积分时间的分析仪来降低噪声。然而，经验系数的使用导致了 REA 方法的不确定性。使用在东亚三个森林地点获得的一年数据集来调查温度的一致性：温带常绿针叶林、热带常绿阔叶林和冷温带落叶针叶林。在不稳定条件下，观测值从 0.54 变化到 0.57。尽管各站点之间的观察值 b 的值在狭窄范围内，但特定站点之间存在轻微差异。我们引入了b的新表达式，相似性b，基于标量相似性，使用积分湍流特性来研究b的性质。在稳定条件下，当垂直风速标准偏差值较低时，观测值和相似性都随着大气稳定性的增加而增加。不同地点的边界稳定条件的变化不同。所有站点的观测均无季节性变化。因此，本研究建议确定每个地点不稳定条件的系数b，并考虑与大气稳定性相关的变化b，以尽量减少REA方法中的误差。
The relaxed eddy accumulation (REA) method is an attractive alternative to the eddy covariance method to measure trace-gas flux, because it allows the use of analyzers with an optimal integration time to reduce the noise. However, the use of an empirical coefficientbresults in uncertainties in the REA method. The consistency ofbfor temperature was investigated using a 1 year dataset obtained at three forest sites in East Asia: a temperate evergreen coniferous forest, a tropical evergreen broadleaf forest, and a cool-temperate deciduous coniferous forest. The observationalbranged from 0.54 to 0.57 under unstable conditions. Although the values for observationalbwere within narrow ranges among the sites, there were slight site-specific differences. We introduced new expression ofb, similarityb, based on scalar similarity using the integral turbulence characteristics to investigate the nature ofb. Both the observational and similaritybincreased with increasing atmospheric stability under stable conditions, when lower values for the standard deviation of the vertical wind velocity resulted in higher values forb. The variations inbunder stable conditions differed among sites. There were no seasonal variations in the observationalbat all sites. Consequently, the present study recommends determining the coefficientbfor unstable conditions for each site and considering changes inbassociated with atmospheric stability in order to minimize errors in the REA method.