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    Please use this identifier to cite or link to this item: http://ir.lib.ncu.edu.tw/handle/987654321/65007

    Title: 應用渦流相關法與權重渦流累積法計算地表通量;Application of Eddy Covariance Method and Relaxed Eddy Accumulation Method on Estimating Surface Fluxes
    Authors: 許適棋;Hsu,Shih-Chi
    Contributors: 水文與海洋科學研究所
    Keywords: 渦流相關法;權重渦流累積法;地表通量;Eddy Covariance Method;Relaxed Eddy Accumulation Method;Surface Flux
    Date: 2014-08-26
    Issue Date: 2014-10-15 14:37:59 (UTC+8)
    Publisher: 國立中央大學
    Abstract: 本研究將高頻之三維超音波風速計、水氣與二氧化碳濃度資料,以渦流相關法(EC)與權重渦流累積法(REA)兩種通量觀測技術進行計算評估。目前公認最能準確估計通量的技術為渦流相關法,但由於所需儀器成本相對上較為昂貴,而權重渦流累積法雖然不需要高頻之氣體分析儀,但需要給定若干控制參數方可進行通量估算,且目前尚無商品化之完整觀測套件可供使用,但近年來在量溫室氣體通量的監測上已有越來越多之應用。本研究將EC所計算出的通量作為比較基準,探討REA中的滯區(deadband)與經驗係數(b)之變化特徵。
    ;This study uses high resolution time series (10Hz) of wind components (u, v, w), sonic temperature (Ts), carbon dioxide (CO2), and vapor(H2O) density data to compute surface fluxes with application of Eddy Covariance method (EC) and Relaxed Eddy Accumulation method (REA). Eddy Covariance method is the most accurate method for measuring surface fluxes at the atmospheric boundary layer. However, the cost of fast response equipment required for EC measurement is very expensive for some trace gases. Recently, REA measurement, without the need of fast response equipment, is widely applied to measure greenhouse gas flux. Nevertheless, this method requires setting parameters before estimating, and has not yet been commercialized. This study takes flux es estimated by the EC method to discuss characteristics of empirical constant (b) and deadband (wd) required in REA techniques.
    Observation data in 2012 was used to help determine the adequate deadband and empirical constant setting of REA with referenced fluxes estimated by EC. Observation data in 2013 was used to verify obtained REA parameter setting. Standard deviation of b is smaller with the deadband set as 0.6 to 0.8 times standard deviation of vertical wind speed. For vapor and carbon dioxide fluxes, using b value of sensible heat and eliminating data with vapor flux differences ranging between -20 and 100 m-mole/m3 or with carbon dioxide flux differences ranging between 0.05 and -0.2 m-mole/m3 can obtain good result. Comparing the surface flux calculated by Eddy Covariance method and Relaxed Eddy Accumulation method, the R-squared values are 0.98, 0.88, and 0.90 in sensible heat, vapor, and carbon dioxide fluxes, respectively. This study provides analysis of deadband and b value of great benefit to actual assembly of REA system in the future.
    Appears in Collections:[水文與海洋科學研究所] 博碩士論文

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