Comparison of sonic anemometer performance under foggy conditions
Comparison of sonic anemometer performance under foggy conditions
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DOI：
10.1016/j.agrformet.2013.01.005
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发表时间：
2013-04
影响因子：
6.2
通讯作者：
T. El-Madany;F. Griessbaum;G. Fratini;J. Juang;Shih-Chieh Chang;O. Klemm
中科院分区：
文献类型：
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作者：
T. El-Madany;F. Griessbaum;G. Fratini;J. Juang;Shih-Chieh Chang;O. Klemm
为了评估雾对音速风速计性能的影响，我们在台湾的一个山区云林点进行了音速风速计的比较，特别强调了它们在涡旋协方差应用中的应用。四个声波风速计(Campbell CSAT3、Gill R3-50、METEK USA-1和R.M.Young 81000VRE)连续15天进行了测试，总雾化持续时间为86小时。分析了4个方面：(1)雾和非雾条件下的尖峰统计；(2)16次雾事件前、中、后的光谱和共谱分析；(3)风和温度的湍流特征之间的相关性；(4)通量误差估计。与能见度高于1000米的情况相比，能见度低于1000米时，所有音速风速计都会产生更多的尖峰。然而，雾造成的总体尖峰数量通常很低，因此与任何测试的声速风速计无关。频谱分析表明，对于大多数风速计来说，雾主要影响音速温度的频谱。在这里，高频范围要么被抑制，要么被放大。这些效果随着雾的持续时间和密度的增加而恶化。对于81000VRE和USA-1，在大雾期间，三个风分量谱、声速温度谱以及w‘t’和w‘u’的协谱都在高频范围内表现出白噪声。CSAT3只在声温和W‘t’的共谱的高频范围内显示出噪声。R3-50对雾的敏感度最小。然而，所产生的通量的差异通常小于测量的通量误差。由于光谱分析的结果和较小的通量误差，R3-50似乎最适合在浓雾条件下进行涡旋协方差测量和过程研究。
A sonic anemometer comparison was performed at a mountain cloud forest site in Taiwan to evaluate the effect of fog on sonic anemometers performance, with particular emphasis to their employment in eddy-covariance applications. Four sonic anemometers (Campbell CSAT3, Gill R3-50, METEK USA-1, and R.M. Young 81000VRE) were tested for 15 consecutive days with an overall fog duration of 86h. Four aspects were analyzed: (1) spike statistics during foggy and non-foggy conditions, (2) spectral and co-spectral analyses before, during, and after 16 fog events, (3) correlations between turbulence characteristics of wind and temperature, and (4) flux error estimations. All sonic anemometers produce more spikes when the visibility is below 1000m, compared to conditions with visibilities above 1000m. However, the overall number of spikes caused by fog is generally low and therefore of no concern for any of the tested sonic anemometers. Spectral analyses showed that for most anemometers fog mostly affects spectra of the sonic temperature. Here, the high frequency range is either damped or amplified. These effects worsen with increasing duration and density of fog. In case of the 81000VRE and the USA-1, all three wind component spectra, sonic temperature spectra as well as the co-spectra of w’T’ and w’u’ show white noise in the high frequency range during dense fog. The CSAT3 shows noise only in the high frequency range of the sonic temperature and the co-spectra of w’T’. Smallest sensitivity to fog was observed for the R3-50. Nevertheless, differences in resulting fluxes are usually smaller than the flux error of the measurements. Due to the results of the spectral analysis and small flux errors the R3-50 seems to be suited best for eddy covariance measurements and process studies under dense foggy conditions.