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	Comparison of flux measurement by open-path and close-path eddy covariance systems
	Song X. ; Yu G. R. ; Liu Y. F. ; Sun X. M. ; Ren C. Y. ; Wen X. F.
	2005
关键词	eddy covariance technique open-path eddy covariance close-path eddy covariance delay time spectrum analyze flux co2 analyzers water-vapor carbon-dioxide forest exchange field fluctuations surface sensor
英文摘要	For flux measurement, the eddy covariance technique supplies a possibility to directly measure the exchange between vegetation and atmosphere; and there are two kinds of eddy covariance systems, open-path and close-path systems. For the system error, it may result in difference of flux measurements by two systems. Therefore, it is necessary to compare the measured results from them. ChinaFLUX covers of eight sites applied the micrometeorological method, in which Changbai Mountains (CBS) and Qianyanzhou (QYZ) carried out open-path eddy covariance (OPEC) and close-path eddy covariance (CPEC) measurements synchronously. In this paper the data sets of CBS and QYZ were employed. The delay time of close-path analyzer to the open-path analyzer was calculated; the spectra and cospectra of time-series data of OPEC and CPEC were analyzed; the open-path flux measurement was used as a standard comparison, the close-path flux measurement results were evaluated. The results show that, at two sites the delay time Of CO2 density for close-path analyzer was about 7.0-8.0 s, H2O density about 8.0-9.0 s; the spectrum from the open-path, close-path and 3D sonic anemometer was consistent with the expected -2/3 slope (log-log plot), and the cospectra showed the expected slope of -4/3 in the internal subrange; the CO2 flux measured by the close-path sensor was about 84% of that of open-path measurement at QYZ, about 80% at CBS, and the latent heat flux was balanced for two systems at QYZ, 86% at CBS. From the flux difference between open-path and close-path analyzers, it could be inferred that the attenuation of turbulent fluctuations in flow through tube of CPEC affected H2O flux more significantly than CO2 flux. The gap between two systems was bigger at CBS than at QYZ; the diurnal variation in CO2 flux Of two measurement systems was very consistent.
出处	Science in China Series D-Earth Sciences
卷	48
页	74-84
收录类别	SCI
语种	英语
ISSN号	1006-9313
内容类型	SCI/SSCI论文
源URL	[http://ir.igsnrr.ac.cn/handle/311030/23059]
专题	地理科学与资源研究所_历年回溯文献
推荐引用方式 GB/T 7714	Song X.,Yu G. R.,Liu Y. F.,et al. Comparison of flux measurement by open-path and close-path eddy covariance systems. 2005.

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