黑河生态水文遥感试验：水文气象观测网数据集（大沙龙站涡动相关仪-2014）

该数据集包含了2014年1月1日至2014年12月31日的黑河水文气象观测网上游大沙龙站涡动相关仪观测数据。站点位于青海省祁连县，下垫面是高山草地。观测点的经纬度是98.9406E, 38.8399N，海拔3739 m。涡动相关仪的架高4.5m，采样频率是10Hz，超声朝向是正北向，超声风速温度仪（CSAT3）与CO2/H2O分析仪（Li7500）之间的距离是15cm。
涡动相关仪的原始观测数据为10Hz，发布的数据是采用Eddypro软件处理的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Eddypro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原始数据中每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。因仪器漂移等原因引起的可疑数据用红色字体标识。10月20日后由于存储卡存储数据问题，导致10Hz数据缺失，由采集器输出的30min通量数据替代。
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），稳定度Z/L（无量纲），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三级（质量标识0:（Δst <30, ITC<30）; 1: （Δst <100, ITC<100）; 其余为2）。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。
水文气象网或站点信息请参考Liu et al. (2018)，观测数据处理请参考Liu et al.(2011)。

This dataset contains eddy covariance observations from the upstream Dashalong Station of the Heihe River Hydrometeorological Observation Network, covering the period from January 1, 2014 to December 31, 2014. The station is located in Qilian County, Qinghai Province, with an underlying surface of alpine grassland. The observation site has geographic coordinates of 98.9406°E, 38.8399°N, and an elevation of 3739 m. The eddy covariance system has an installation height of 4.5 m, a sampling frequency of 10 Hz, and the ultrasonic transducer is oriented towards true north. The distance between the ultrasonic anemometer/thermometer (model CSAT3) and the CO2/H2O analyzer (model Li7500) is 15 cm.

The raw observational data from the eddy covariance system are at 10 Hz. The released dataset consists of 30-minute averaged data processed using the EddyPro software. The primary processing steps include: outlier removal, time lag correction, double coordinate rotation, frequency response correction, ultrasonic virtual temperature correction, and Webb-Pearman-Leuning (WPL) density correction. Quality assessments were conducted for each flux product, mainly including tests of atmospheric stationarity (Δst) and turbulence similarity characteristics (ITC). Additional screening was applied to the 30-minute flux outputs from EddyPro: (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 exceeding 10% per 30-minute segment of 10 Hz raw data; (4) Remove nocturnal weak turbulence observations (friction velocity u* < 0.1 m/s).

The observational data have an averaging period of 30 minutes, yielding 48 data points per day. Missing data are marked as -6999. Suspicious data caused by factors such as instrument drift are marked in red font. After October 20, 2014, due to storage issues with the on-site memory card, 10 Hz raw data were unavailable, so 30-minute flux data output by the data logger were used as a substitute.

The released observational data include the following variables: Date/Time, Wind Direction (Wdir, °), Horizontal Wind Speed (Wnd, m/s), Standard Deviation of Lateral Wind Speed (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), Stability Parameter (Z/L, dimensionless), Sensible Heat Flux (Hs, W/m²), Latent Heat Flux (LE, W/m²), Carbon Dioxide Flux (Fc, mg/(m²·s)), Quality Flag for Sensible Heat Flux (QA_Hs), Quality Flag for Latent Heat Flux (QA_LE), and Quality Flag for Carbon Dioxide Flux (QA_Fc). The quality flags for sensible heat, latent heat, and carbon dioxide fluxes are divided into three levels: 0: (Δst < 30, ITC < 30); 1: (Δst < 100, ITC < 100); and 2 for all other cases. The meaning of the data timestamp: for example, 0:30 represents the average value of the 0:00-0:30 period. All data are stored in *.xls format.

For information on the hydrometeorological network and the study site, please refer to Liu et al. (2018); for detailed data processing procedures, please refer to Liu et al. (2011).