EBEX-2000湍流热通量订正和地表能量平衡闭合问题研究

A Study of Turbulent Heat Flux Corrections and Energy Balance Closure Problem on the Surface Layer in EBEX-2000

运用EBEX-2000实验资料,分析超声虚温订正和Webb订正对湍流热通量计算的影响及这两种订正的主要控制因子,并在对湍流热通量进行修正的基础上简单讨论了能量平衡闭合率（EBR）的影响因子,结合实际的天气、地形条件给出了比较合理的解释。研究结果表明：超声虚温订正值为–40~2 W/m^2,有明显日变化,均值为8 W/m^2,主要受大气稳定度和水汽垂直梯度影响;Webb订正值范围为5~14 W/m^2,订正量均值较小,约1.8 W/m^2,白天为正值,夜间为负值,主要受波文比和空气比湿的影响,出现较大修订值的几率很小;30min平均的能量平衡闭合比率（EBR）约为0.63,其日变化幅度剧烈,日变化幅度及夜间离散度很大,并且随土壤含水量的突然上升而急剧下降。

Data of EBEX-2000 was used to analyze the influences of Schotanus correction and Webb correction on turbulent heat fluxes and the governing factors of the two corrections.Furthermore,considering turbulent heat flux corrections,impact factors of energy balance ratio（EBR） were discussed and reasonable interpretations were provided according to actual weather and topographic condition.Results show that the magnitude of Schotanus correction varies from 40 to 2 W/m^2,with a significant diurnal variation,and the mean value of which is 8 W/m^2.The two dominant factors of Schotanus correction are atmospheric stability and vertical gradient of water vapor.The magnitude of Webb correction varies from 5 W/m^2to 14 W/m^2 with a mean value of 1.8 W/m^2,which is much smaller than that of Schotanus correction.Webb correction is positive for daytime and negative for nighttime,and it is mainly affected by Bowen ratio and specific humidity,having little probability to reach a great value.EBR calculated using a 30 minutes average is about 0.63 with large diurnal variations and dispersion,and decreases rapidly with a sudden rise of soil water content.