Variability of the Structure Parameters of Temperature and Humidity Observed in the Atmospheric Surface Layer Under Unstable Conditions
Variability of the Structure Parameters of Temperature and Humidity Observed in the Atmospheric Surface Layer Under Unstable Conditions
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DOI：
10.1007/s10546-013-9882-2
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发表时间：
2014-03
影响因子：
4.3
通讯作者：
M. Braam;A. Moene;F. Beyrich
中科院分区：
文献类型：
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作者：
M. Braam;A. Moene;F. Beyrich
温度和湿度的结构参数在折射率测量中是重要的，因为它们决定了空气折射率的结构参数，空气折射率是用折射率计获得的主要大气变量。在这项研究中，我们调查的莫宁-奥布霍夫标度的结构参数（表示为）的温度和湿度的对数的变化。我们使用的观测涡度协方差系统在三个高度（2.5，50和90米）在大气表层不稳定的条件下。的可变性取决于不稳定性和计算的平均窗口的大小。如果不稳定性增加，向上运动（大）和向下运动（小）之间的差异就会增加。然而，差异是不够大，导致双峰概率密度函数。如果平均窗口大小增加，则的方差减小。的方差与平均窗口大小的各种稳定性类的线性回归显示的偏移和斜率（在绝对意义上）的增加与增加的不稳定性。对于温度，来自三个高度的数据显示了可比的结果。相反，对于湿度，偏移和斜率在50和90 m处大于2.5 m处。最后，我们讨论了如何利用这些发现来评估沿风速计路径或飞机飞行段观测到的差异是否在局部变化的范围内，或者是否可以归因于表面异质性。这对于解释在非均匀表面上测量的数据是重要的。
The structure parameters of temperature and humidity are important in scintillometry as they determine the structure parameter of the refractive index of air, the primary atmospheric variable obtained with scintillometers. In this study, we investigate the variability of the logarithm of the Monin-Obukhov-scaled structure parameters (denoted as) of temperature and humidity. We use observations from eddy-covariance systems operated at three heights (2.5, 50, and 90 m) within the atmospheric surface layer under unstable conditions. The variability ofdepends on instability and on the size of the averaging window over whichis calculated. If instability increases, differences inbetween upward motions (large) and downward motions (small) increase. The differences are, however, not sufficiently large to result in a bimodal probability density function. If the averaging window size increases, the variances ofdecrease. A linear regression of the variances ofversus the averaging window size for various stability classes shows an increase of both the offset and slope (in absolute sense) with increasing instability. For temperature, data from the three heights show comparable results. For humidity, in contrast, the offset and slope are larger at 50 and 90 m than at 2.5 m. In the end we discuss how these findings could be used to assess whether observed differences inalong a scintillometer path or aircraft flight leg are just within the range of local variability inor could be attributed to surface heterogeneity. This is important for the interpretation of data measured above a heterogeneous surface.