Open- vs. closed-path eddy covariance measurements of the net ecosystem carbon dioxide and water vapour exchange: a long-term perspective.
Open- vs. closed-path eddy covariance measurements of the net ecosystem carbon dioxide and water vapour exchange: a long-term perspective.
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DOI：
10.1016/j.agrformet.2008.08.011
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发表时间：
2009-02
影响因子：
6.2
通讯作者：
Wohlfahrt, Georg
中科院分区：
文献类型：
--
作者：
Haslwanter, Alois;Hammerle, Albin;Wohlfahrt, Georg
开放(OP)和闭路(CP)涡旋协方差系统的差异设计、部署和数据后处理是正在进行的全球通量合成活动的潜在偏差来源。在这里，我们使用一个独特的六年同步CP和OP二氧化碳(CO2)和水汽(H2O)涡旋协方差通量测量的数据集，在奥地利温带山地草原上空探索这些差异在长期基础上的后果。基于理论的传递函数方法能够考虑并纠正两个系统在低通滤波方面的差异。校正后的CO2和H2O通量具有很好的1：1对应关系，但在高气温、高风速、高总辐射、大太阳角和低相对湿度的条件下，CP系统倾向于低估OP H2O通量。对OP红外线气体分析仪自加热的修正对这些关系的影响很小。能量平衡关闭对OP系统略有利。两个系统的随机流量不确定性没有显著差异。由于水和雪对红外线路径的阻碍，不得不排除更大比例的OP数据。然而，这并没有相应地转化为接受的CP通量值的更大比例，因为在平稳性测试中有更大比例的CP通量数据不合格。在整个年度循环中，与OP系统相比，CP系统平均产生更积极的净生态系统二氧化碳交换(25vs.0 gcm−2 y−1)和更低的蒸散量(465vs.549 mm y−1)。
The differential design, deployment and data post-processing of open- (OP) and closed-path (CP) eddy covariance systems is a potential source of bias for ongoing global flux synthesis activities. Here we use a unique six year data set of concurrent CP and OP carbon dioxide (CO2) and water vapour (H2O) eddy covariance flux measurements above a temperate mountain grassland in Austria to explore the consequences of these differences on a long-term basis. The theoretically based transfer function approach was able to account and correct for the differences in low-pass filtering between the two systems. Corrected CO2 and H2O fluxes exhibited excellent 1:1 correspondence, but the CP system tended to underestimate OP H2O fluxes during conditions of high air temperature, wind speed and global radiation, large sun angles and low relative humidity. Corrections for self-heating of the OP infra-red gas analyser had a very small effect on these relationships. Energy balance closure was slightly more favourable for the OP system. No significant differences were found for the random flux uncertainty of both systems. A larger fraction of OP data had to be excluded because of obstructions of the infra-red path by water and snow. This, however, did not translate into a correspondingly larger fraction of accepted CP flux values, because of a larger percentage of CP flux data failing on the stationarity test. Integrated over the annual cycle, the CP system yielded on average a more positive net ecosystem CO2 exchange (25 vs. 0 gC m−2 y−1) and a lower evapotranspiration (465 vs. 549 mm y−1) as compared to the OP system.
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影响因子：
6.2
作者：
Ibrom, Andreas;Dellwik, Ebba;Pilegaard, Kim
通讯作者：
Pilegaard, Kim
DOI：
10.5194/bg-5-421-2008
发表时间：
2008-03-20
期刊：
Biogeosciences (Online)
影响因子：
--
作者：
Hammerle A;Haslwanter A;Tappeiner U;Cernusca A;Wohlfahrt G
通讯作者：
Wohlfahrt G
影响因子：
6.2
作者：
Grelle, Achim;Burba, George
通讯作者：
Burba, George
影响因子：
6.2
作者：
Gu, LH;Falge, EM;Xu, LK
通讯作者：
Xu, LK
影响因子：
4.3
作者：
Kowalski, Andrew S.;Serrano-Ortiz, Penelope
通讯作者：
Serrano-Ortiz, Penelope