涡动相关仪观测数据的处理与质量评价研究

涡动相关仪能够较准确地直接测量地表—大气间的湍流交换，在世界范围内得到了广泛的应用。但它的使用是有条件限制的，如果不进行必要的修正，得到的通量就可能有较大的误差。以密云观测站一年的涡动相关仪观测数据为例进行分析。结果表明：野点值剔除、坐标旋转以及超声温度订正对地表感热、潜热等通量的测量结果影响均在±1%之内，但坐标旋转对动量通量影响较大，必须对潜热和CO2通量进行空气密度效应订正；湍流谱在惯性副区基本满足-2/3次方定律，协谱基本满足-4/3次方定律。经过对观测数据的筛选和处理后，约75%的观测数据质量较好，2%的数据需要剔除。通量贡献源区分析表明，全天和白天均有超过70%的通量源区落在感兴趣区域内，超过90%的通量贡献最大点落在感兴趣区域内。

A Study on the Data Processing and Quality Assessment of the Eddy Covariance System

The eddy covariance (EC) technique can measure turbulent exchanges between surface and atmosphere directly, and is now used widely in all of the flux stations. Since this method is based on certain assumptions, the obtained surface fluxes are not true values if there are no necessary corrections. Recent development and some focal points of the eddy covariance method are reviewed, and used in the processing of the data collected in Miyun station, which is one of the flux stations near Beijing. The analysis of EC data at Miyun station shows: Despiking and the sonic temperature and coordinate rotation corrections have a rather little effects on the surface sensible and latent fluxes (about 1%), however, coordinate rotation has large effect on the momentum flux. The air density correction (WPL correction) is important for water vapor and CO^₂ fluxes, and should be applied. The turbulent spectral checks in the data quality evaluation are satisfactory. Turbulence stationarity and integral characteristics are used in the flux data quality analysis. After rigorously data screening, the final result shows that about 75% flux data is good, and 2% flux data need to be discarded. Footprint analysis shows for all day and daytime periods, over 70% source area of the fluxes is located in the interested area (non mountainous region) with over 90% of the biggest contribution points in the area.