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目前广泛使用的涡度相关系统开路CO_2/H_2O分析仪存在表面加热效应,可能影响涡动通量测量精度.以帽儿山森林生态站温带落叶林的开路涡度相关系统为例,采用细丝热电偶评估了开路CO_2/H_2O分析仪(Li-7500)的加热效应,并检验Burba方程的适用性.结果表明:2016年4月23日至5月28日,白天Li-7500光路中部温度比环境空气温度高0.2℃以上,夜间二者很接近,加热峰值多出现在清晨转换期和正午或午后.Burba第4种方法的一元模型(Burba LF)估计的感热通量加热效应(H_(S,HE))日变化大体呈矩形波型,多元线性回归模型(Burba MR)的估计值呈微弱的单峰型.与K079型细丝热电偶(单裸丝线径0.079 mm)测定(K079)和细丝热电偶模拟(K079Model)的感热通量相比,Burba LF和Burba MR估算的白天变化小且波峰低而宽(20 W·m~(-2)),昼夜过渡急剧,夜间一般低于5 W·m~(-2).K079和K079Model法的HS,HE峰值在40 W·m~(-2)以上,夜间HS,HE在零值上下波动.白天Li-7500光路的感热通量增量为13.6%.K079和K079Model估算的白天加热对CO_2湍流通量影响(F_(c,HC))的平均值约0.5 mg CO_2·m~(-2)·s-1,是以往估值的2倍.与实测法相比,Burba方程正午由于H_(S,HE)不足而低估了F_(c,HC),但因高估了清晨、傍晚和夜间加热效应,导致整体上高估F_(c,HC).研究结果证实K079和K079Model法均可用于估计F_(c,HC).
The currently widely used open-circuit CO_2 / H_2O analyzer for eddy covariance system has the effect of surface heating, which may affect the accuracy of eddy flux measurement.As an example of the open-eddy covariance system of temperate deciduous forest at Maoershan Forest Ecological Station, The thermocouple evaluated the heating effect of the open CO_2 / H_2O analyzer (Li-7500) and tested the applicability of the Burba equation.The results show that the temperature of Li-7500 mid-temperature in the daytime from April 23 to May 28, 2016 Ambient air temperature is higher than 0.2 ℃, and the two are close at night, and the heating peak appears mostly in the morning and midday or in the afternoon.The sensible heat flux heating effect estimated by the Burba LF method (H_ ( (K079) with a K079 type filament thermocouple (single bare wire diameter of 0.079 mm) was used to estimate the daily variation of the Burba MR model. Compared with the sensible heat flux of the K079Model, Burba LF and Burba MR show a small day-to-day variation with a low and wide peak (20 W · m -2), a sharp transition from day to night and nighttime Less than 5 W · m -2 .The HS and HE peak values of K079 and K079Model were above 40 W · m -2, The value of sensible heat flux increased by 13.6% for the Li-7500 light path in the daytime, and the average value of F_ (c, HC) estimated by K079 and K079Model for the CO_2 turbulent flux was about 0.5 mg CO_2 · Compared with the experimental method, Burba equation underestimates F_ (c, HC) due to the lack of H_ (S, HE) The early morning, evening and night heating effects resulted in overestimation of F_ (c, HC). The results of the study confirm that K079 and K079Model methods can be used to estimate F_ (c, HC).