海河流域多尺度地表通量与气象要素观测数据集：大兴站-涡动相关仪（2008-2010）

该数据集包含了2008年1月1日至2010年12月31日的涡动相关仪观测数据。站点位于北京市大兴区魏善庄，下垫面是玉米/小麦、瓜果。观测点的经纬度是116.4271E，39.6213N，海拔20m。
涡动相关仪的采集频率是10Hz，架高为3m，超声朝向是295度（正北向为0度），超声风速仪与CO2/H2O分析仪之间的距离是18cm。发布的数据是采用Edire软件对原始采集的10Hz数据进行后处理得到的30分钟数据，其处理的主要步骤包括：野点值剔除，延迟时间校正，坐标旋转（平面拟合法），频率响应修正，超声虚温修正和密度（WPL）修正等。同时对各通量值进行质量评价，主要是大气平稳性（Δst）和湍流相似性特征（ITC）的检验。对Edire软件输出的30min通量值也进行了筛选：（1）剔除仪器出错时的数据；（2）剔除降水前后1h的数据；（3）剔除10Hz原始数据每30min内缺失率大于3%的数据；（4）剔除夜间弱湍流的观测数据（u*小于0.1m/s）。观测数据的平均周期为30分钟，一天48个数据，缺失数据标记为-6999。
涡动相关仪发布的观测数据包括：日期/时间Date/Time，风向Wdir（°），水平风速Wnd（m/s），侧向风速标准差Std_Uy（m/s），超声虚温Tv（℃），水汽密度H2O（g/m3），二氧化碳浓度CO2（mg/m3），摩擦速度Ustar（m/s），奥布霍夫长度，感热通量Hs（W/m2），潜热通量LE（W/m2），二氧化碳通量Fc（mg/(m2s)），感热通量的质量标识QA_Hs，潜热通量的质量标识QA_LE，二氧化碳通量的质量标识QA_Fc。感热、潜热、二氧化碳通量的质量标识分为九级（质量标识1：（0<Δst<15, 0< ITC<30）; 2：（16<Δst<30, 0< ITC<30）; 3：( 0<Δst<30, 31< ITC<75); 4：（31<Δst<75, 0< ITC<30）; 5：（0<Δst<75, 31< ITC<100）; 6：（76<Δst<100, ITC<100）; 7：（Δst<250, ITC<250）; 8：（Δst<1000, ITC<1000）; 其余为9）。数据时间的含义，如0:30代表0:00-0:30的平均；数据以*.xls格式存储。
观测试验或站点信息请参考 Jia et al,(2012)，数据处理请参考Liu et al.(2013)。

This dataset contains eddy covariance observations collected from January 1, 2008 to December 31, 2010. The monitoring site is located in Weishanzhuang, Daxing District, Beijing, with underlying surfaces covered by corn/wheat and melons and fruits. The geographic coordinates of the observation point are 116.4271°E, 39.6213°N, and the elevation is 20 m.

The eddy covariance system has a sampling frequency of 10 Hz, an installation height of 3 m, an ultrasonic anemometer orientation of 295 degrees (true north is defined as 0 degrees), and the distance between the ultrasonic anemometer and the CO2/H2O analyzer is 18 cm. The released data are 30-minute flux data processed from the raw 10-Hz observations using Edire software. The main processing steps include: outlier removal, time lag correction, coordinate rotation (planar fit method), frequency response correction, ultrasonic virtual temperature correction, and density (WPL) correction. Quality assessments were also conducted for each flux value, mainly including tests of atmospheric stationarity (Δst) and turbulence similarity characteristics (ITC). Further screening was performed on the 30-minute flux outputs from Edire software: (1) remove data collected during instrument failures; (2) remove data within 1 hour before and after precipitation events; (3) remove data with a missing rate greater than 3% per 30-minute window of raw 10-Hz data; (4) remove nighttime weak turbulence observations with friction velocity u* < 0.1 m/s. The average sampling period of the observational data is 30 minutes, with 48 data records per day, and missing data are marked as -6999.

The released eddy covariance observation data include: Date/Time, wind direction Wdir (°), horizontal wind speed Wnd (m/s), lateral wind speed standard deviation Std_Uy (m/s), ultrasonic virtual temperature Tv (℃), water vapor density H2O (g/m³), carbon dioxide concentration CO2 (mg/m³), friction velocity Ustar (m/s), Obukhov length, sensible heat flux Hs (W/m²), latent heat flux LE (W/m²), carbon dioxide flux Fc (mg/(m²s)), quality flag of sensible heat flux QA_Hs, quality flag of latent heat flux QA_LE, and quality flag of carbon dioxide flux QA_Fc. The quality flags for sensible heat, latent heat, and carbon dioxide fluxes are divided into 9 levels:
1: (0 < Δst < 15, 0 < ITC < 30);
2: (16 < Δst < 30, 0 < ITC < 30);
3: (0 < Δst < 30, 31 < ITC < 75);
4: (31 < Δst < 75, 0 < ITC < 30);
5: (0 < Δst < 75, 31 < ITC < 100);
6: (76 < Δst < 100, ITC < 100);
7: (Δst < 250, ITC < 250);
8: (Δst < 1000, ITC < 1000);
9: all other cases.

The timestamp indicates the averaging period, e.g., 0:30 represents the average value from 0:00 to 0:30. All data are stored in *.xls format.

Please refer to Jia et al. (2012) for details of the observational experiment and site information, and Liu et al. (2013) for the data processing procedures.