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| DOI：10.13522/j.cnki.ggps.20170007 |
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| Improving the Accuracy of Water and Thermal Fluxes Calculated for Maize Field Using Coordinate Rotation Method |
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YANG Danni, CHEN Yan, QIN Shujing, LI Sien
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China Agricultural University, Beijing 100083, China
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| Abstract: |
| 【Objective】 The energy closure rate plays an important role in calculating water and thermal fluxes of farmland in using the eddy covariance data, and this paper investigated the efficacy of using coordinate rotation method to improve the accuracy of the fluxes calculated for a maize field. 【Method】 Latent heat and sensible heat fluxes were measured by the eddy covariance method in the Shiyang River Experimental Station at Wuwei City of Gansu Province from 2015 to 2016; they were then analyzed using the Double Rotation and Triple Rotation methods, as well as the Planar Fit method. 【Result】 There was no noticeable difference between the energy closure rates calculated by the Double Rotation and Triple Rotation methods, yet the correlation between the turbulent flux and the effective energy after incorporating the Triple Rotation method was improved. The Planar Fit method was more suitable for places where the underlying surface is uniformly flat, the turbulent exchange was stable and the advection was weak. In contrast, the Double Rotation and Triple Rotation methods worked better for complex terrains. In our experiment, the calculated energy closure rate of water and thermal fluxes for mulched maize field with border irrigation was higher than for mulched maize field with drip irrigation by 5%~8% and the mean turbulent flux was 2%~17% higher, with the root mean square error for the turbulent flux and effective energy in the former being 12%~23% lower than that in the latter. 【Conclusion】 In our experimental field, the Planar Fit method is appropriate to calculate the eddy-covariance water and thermal flux in terms of tilt correction for mulched field with border irrigation, while the Triple Rotation method works better for mulched field with drip irrigation. |
| Key words: eddy covariance; energy closure rate; Double Rotation method; Triple Rotation method; Planar Fit method |
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