亚热带稻田能量平衡闭合状况分析

通过采用线性回归，能量平衡比率和相对残差频率分布3种统计方法对涡度相关法通量观测的稻田能量平衡闭合状况进行了评价，并分析了能量平衡闭合程度的季节变化趋势。结果表明，在稻田生态系统中存在能量不闭合现象，年能量平衡比率为0.87，年平均不闭合程度为13%；能量平衡比率在5—8月份平均为0.85，能量不闭合程度较高；1—4月份和9—12月份平均为0.92，不闭合程度较低。在假定常规的有效能量测定正确的前提下，可以认为涡度相关测定的湍流通量可能被低估了

Energy Balance Closure at Rice Paddy Fields in Subtropical Region

Eddy covariance (EC) method measuring carbon and energy fluxes provides a unique contribution to the study of the environmental, biological and climatological controls of net surface exchange between vegetation and the atmosphere. Independent methods of evaluating the reliability of the eddy covariance measurements at different ecosystem sites are highly desirable. From 2003, EC technique was used in rice paddy fields to measure carbon flux, latent (LE) and sensible (H) heat flux, the net radiation (Rn) and the heat flux (G) into the soil substrate. In the research, the objectives were to assess the accuracy of eddy covariance method, evaluate the energy balance closure and analyze the change trend during the whole year. Energy balance closure was evaluated by statistical methods of ordinary linear regression, energy balance ratio (the ratio of turbulent energy fluxes to available energy, viz. LE and H against Rn less G) and remnant frequency distribution. These methods indicate a general lack of closure during the whole year, with a mean imbalance of 13% or energy balance ratio of 0.87. The imbalance was greater (15%) during from May to Aug than the other period during the year (8%). The results suggest that estimates of the scalar turbulent fluxes of sensible and LE were underestimated and/or that available energy is overestimated.