利用细丝热电偶评估涡度相关系统开路分析仪表面加热效应  

Assessing the surface heating effect of the open-path analyzer of an eddy covariance system with fine-wire thermocouples

作　　者：王兴昌[1] 王传宽[1] 刘帆[1] 甄晓杰 

机构地区：[1]东北林业大学生态研究中心,哈尔滨150040 [2]北京天诺基业科技有限公司,北京100089

出　　处：《应用生态学报》2017年第3期983-991,共9页Chinese Journal of Applied Ecology

基　　金：国家自然科学基金项目(41503071);中央高校基本科研业务费专项(2572016BA03);教育部长江学者和创新团队发展计划项目(IRT_15R09)资助~~

摘　　要：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 open-path CO2/H2O analyzer that is currently widely used in the eddy covariance （EC） system possesses a surface heating effect, which may influence the accuracy of the eddy-flux measurements. Taking the open-path EC system in the temperate deciduous forest of the Maoershan Ecosystem Research Station as a case, we assessed the beating effect of the open-path CO2/H2O analyzer （Li-7500） with fine-wire thermoeouples and tested the applicability of Burba＇ s equations. The results indicated that between April 23 and May 28 in 2016, the daytime air temperature in the midoptical-path of the Li-7500 was on average 0.2 ℃ higher than the ambient air temperature, while the nocturnal temperature was almost equal, with the peak of the heating often occurring in the morning transition period and at noon or in the early afternoon. The diurnal variation in the heating effect on the sensible heat flux （HS,HE） estimated from the simple linear-fitting models in the fourth method by Burba （BurbaLF） was overall a rectangle-like wave, whereas that from the multiple re- gression models （BurbaMR） showed a weak mono-peak shape. Compared with direct measurements （K079） with the K-type fine-wire thermocouples （with a 0.079 mm diameter of single bare wire） and the HS.HE modeled with two fine-wire thermocouples （K079Model）, the estimated HS,HF with the BurbaLF and BurbaMR varied little in the daytime with a lower but wider daytimepeak （20 W· m-2） , a sharp transition between daytime and nighttime, and a typical nocturnal value of 〈 5 W · m-2. The peak values of Hs,HE estimated from the K079 and K079Model could be higher than 40 W · m-2, and the values at night fluctuated around zero. The sensible heat flux in the optical-path of the Li-7500 was increased by 13.6% during the daytime. The value of the daytime heating effect on the CO2 turbulent flux （Fe,HC） estimated from the K079 and K079Model was averaged about 0.5 mg CO2 · m-2 · s-1, twice of the value estimated previously. Compared

关 键 词：开路红外气体分析仪 表面加热效应 光路温度 细丝热电偶 Burba校正 

分 类 号：S758.7[农业科学—森林经理学]