海河流域多尺度地表通量与气象要素观测数据集：怀来站-涡动相关仪（40m塔）-2023

该数据集包含了2023年1月12日至2023年10月21日的40m塔涡动相关仪观测数据。站点位于河北省怀来县东花园镇，下垫面水浇地玉米。观测点的经纬度是115.7923E, 40.3574N，海拔480m。涡动相关仪的采集频率是10Hz，架高为3.5 m，超声朝向是正北向，超声风速仪（CSAT3）与CO2/H2O分析仪（EC150）之间的距离是0 cm。
发布的数据是采用Eddypro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（二次坐标旋转），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。对处理后输出的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10%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。在冬季EC150测量水汽密度出现很多负值，以-6999填充。
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（K），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。感热、潜热、二氧化碳通量的质量标识分为九级（质量标识1-3数据质量好，4-6数据质量较好，7-8数据质量较差（较插补数据好）；9数据质量差）。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Guo et al.(2020)，数据处理请参考Liu et al. (2013)。

This dataset contains eddy covariance system observations collected at a 40-meter tower from January 12, 2023 to October 21, 2023. The observation site is located in Donghuayuan Town, Huailai County, Hebei Province, with an underlying surface of irrigated maize field. The geographic coordinates of the observation point are 115.7923° E, 40.3574° N, and the elevation is 480 m. The eddy covariance system has a sampling frequency of 10 Hz, an installation height of 3.5 m, the ultrasonic anemometer faces true north, and the distance between the sonic anemometer (CSAT3) and the CO2/H2O analyzer (EC150) is 0 cm.

The released data are 30-minute averaged data processed from the original 10 Hz raw data using EddyPro software. The main processing steps include: outlier removal, time lag correction, double coordinate rotation, frequency response correction, sonic virtual temperature correction, and density (WPL) correction, etc. Meanwhile, quality assessment was conducted for each flux value, mainly including tests of atmospheric stationarity (Δst) and turbulent similarity characteristics (ITC). The processed 30-minute flux values were further screened according to the following criteria: (1) Remove data collected during instrument malfunctions; (2) Remove data within 1 hour before and after precipitation events; (3) Remove data with a missing rate greater than 10% in the 10 Hz raw data within each 30-minute period; (4) Remove nighttime weak turbulence observations (u* < 0.1 m/s). The average period of the observation data is 30 minutes, with 48 data points per day. Missing data are marked as -6999. During winter, numerous negative values were recorded in water vapor density measured by EC150, which were filled with -6999.

The released eddy covariance observations include: Date/Time, wind direction Wdir (°), horizontal wind speed Wnd (m/s), lateral wind speed standard deviation Std_Uy (m/s), sonic virtual temperature Tv (K), 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, and quality flag of latent heat flux QA_LE. The quality flags for sensible heat, latent heat, and carbon dioxide fluxes are graded into nine levels: quality levels 1–3 indicate good data quality, 4–6 indicate fair data quality, 7–8 indicate poor data quality (better than interpolated data), and 9 indicates poor data quality. The meaning of the data timestamp: e.g., 0:30 represents the average over the period 0:00–0:30. All data are stored in *.xls format.

Please refer to Guo et al. (2020) for the observation experiment and site information, and Liu et al. (2013) for the data processing procedures.