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坐标旋转对东北山地森林涡动通量的影响

1. 东北林业大学生态研究中心, 哈尔滨 150040
• 收稿日期:2016-04-18 发布日期:2016-09-18
• 通讯作者: * E-mail: wangck-cf@nefu.edu.cn
• 作者简介:王兴昌,男,1982年生,助理研究员,博士研究生. 主要从事森林生态系统碳循环和涡动协方差通量观测研究. E-mail: ecowangxc@126.com
• 基金资助:
国家自然科学基金项目(41503071)和教育部长江学者和创新团队发展计划项目(IRT_15R09)资助

Effects of coordinate rotations on eddy fluxes over a forest on a mountainous terrain in Northeast China.

WANG Xing-chang, WANG Chuan-kuan*

1. Center for Ecological Research, Northeast Forestry University, Harbin 150040, China
• Received:2016-04-18 Published:2016-09-18
• Contact: * E-mail: wangck-cf@nefu.edu.cn
• Supported by:
This work was supported by the Project of National Natural Science Foundation of China (41503071) and the Program for Changjiang Scholars and Innovative Research Team of Ministry of Education (IRT_15R09)

Abstract: Coordinate rotation is an essential step in eddy covariance (EC) flux measurements particularly on complex terrains. Systematically assessing impacts of coordinate rotation methods can improve the accuracy in EC flux estimations. Taking the Maoershan flux tower in a temperate deci-duous forest on valley slopes as a case, we comprehensively examined the effects of various tilt-correction methods on sensible heat flux (H), latent heat flux (LE), CO2 fluxes (Fc), energy ba-lance, friction velocity (u*), and vertical velocity (w) using the standardized major axis method. Compared with the unrotated fluxes, the double rotation (DR), planar fit (PF), vertical velocity unbiased planar fit (NBPF), monthly planar fit (MPF), triple rotation (TR) and monthly sector-wist planar fit (MSWPF) changed the H by +1.5%, +3.8%, +3.1%, +3.3%, -1.3% and -7.1%, respectively. The NBPF and DR increased LE by 1.0% and 0.4%, respectively. The PF also increased LE by 0.671 W·m-2, and the MPF decreased LE by 0.4%, but increased the intercept by 0.747 W·m-2. In contrast, the MSWPF and TR decreased the LE by 4.5% and 15.1%, respectively. The coordinate rotation reduced the Fc by 6.0% (DR)-12.1% (TR). Among the studied methods, the PF increased the energy balance closure by about 2%, whereas the TR decreased it by about 6%. In the light of u* and w, the TR and NBPF were inappropriate for anemometer tilt correction. Considering the precision and practical application of EC measurements, we recommend the PF as the first choice for the Maoershan flux tower site, followed by the DR. These findings are useful for tilt correction of anemometer in EC flux observations over complex terrains.