华北地区冬小麦田水热、二氧化碳和甲烷湍流输送特征的实验研究

本文利用2012年4月30日至5月10日华北地区大气湍流实验资料,分析了冬小麦田下垫面温度、湿度、二氧化碳(CO2)和甲烷(CH4)的湍流统计和输送特征,利用涡旋相关法计算的CH4通量值确定了松弛涡旋累积(REA)法计算CH4通量的经验系数.结果表明,不稳定层结下,温度、湿度、CO2和CH4的归一化标准差随稳定度参数z/L的关系满足-1/3幂次关系.热量、水汽和CO2水平方向的湍流输送和垂直方向的比值与稳定度参数z/L存在一定的相关关系,但CH4没有类似特征.实验期间,感热通量数值较低,潜热通量较高;CO2在夜间表现出微弱的向上输送,其余时段为向下输送,可以认为实验站所在地区是碳汇;CH4的湍流输送整体为向下输送,无明显的日变化规律,可以认为是CH4汇.利用松弛涡旋累积法获取CO2和CH4通量的参数取值分别为0.61和0.30.

Turbulent characteristics of water,heat, carbon dioxide and methane transport over winter wheat fields of North China

Based on the turbulent observations during April 30 and May 10 2012, this work investigated statistical characteristics of atmospheric turbulent and water, heat, carbon dioxide (CO₂) and methane (CH₄) transport in North China. The empirical coefficient used to calculate the flux of CH₄ in the Relaxed Eddy Accumulation (REA) method was simulated. The results show that in unstable conditions, the normalized standard deviations of temperature, humidity, CO₂ and CH₄ are related to z/L following the "-1/3 power law". The ratios between horizontal transport and vertical transport of heat, water vapor and CO₂ are related to z/L, but CH₄ has no similar relationship. Sensible heat flux is quite low while latent heat flux is relatively high. CO₂ flux is slightly above zero during nighttime and below zero during daytime, indicating that the observed area is a carbon sink. CH₄ flux is mainly below zero, indicating that the observed area is a methane sink. The values of the empirical coefficients used to calculate the flux of CO₂ and CH₄ in REA method are 0.61 and 0.30, respectively.