Homogenized, gap-filled, daily air temperature data for Saddle, 1986 - ongoing.

As part of its long-term climate data core collection, the Niwot Ridge LTER has collected daily air temperature at the Saddle site since 1981. The Saddle station is located at 3525 m.a.s.l. and is an important point location to capture local, ambient meteorological conditions for many biological and environmental datasets collected nearby. The location of the Saddle station has also presented challenges to its operation. Freezing temperatures, snow deposition from strong winds following storms, and exposure to lightning are some elements that have disrupted instrument functionality, affected data quality, and made access for research staff difficult over time, especially in winter months. These interruptions have led to missing or faulty data at times and inconsistent data gap-filling. Additionally, a mixture of mechanical hygrothermograph chart and temperature sensors with electronic data loggers have been used since the inception of the Saddle station to measure and record air temperature. Thus, a close inspection of potential influence from instrument turnover and relevant notes from research staff is required for a quality, daily air temperature time series for Saddle.
Here we present a quality-controlled, gap-filled, daily time series of maximum, average, minimum, and diurnal air temperatures that accounts for instrument turnover at the Saddle. Methods follow those used to gap-fill long-term daily air temperature at the Niwot Ridge LTER D1 and C1 stations so there is consistency among core collection daily air temperature datasets. Metadata for this data package centralizes the most complete station history for Saddle air temperature and includes notes to data users on aspects and limitations of the dataset to consider when using these data in scientific analyses.

作为长期气候数据核心馆藏的组成部分，尼沃特岭长期生态研究站点（Niwot Ridge LTER）自1981年起便在萨德尔（Saddle）站点开展每日气温观测。萨德尔站海拔3525米（m.a.s.l.），是捕捉周边诸多生物与环境数据集所需的局地近地面气象条件的关键观测点位。该站点的选址也为运维工作带来了诸多挑战：低温、风暴后强风裹挟的积雪沉积，以及雷击暴露风险，均曾干扰仪器正常运行、影响数据质量，且长期以来给研究人员的现场作业带来困难，冬季尤为突出。此类中断不时导致数据缺失或异常，同时造成数据插补工作缺乏统一标准。此外，自萨德尔站建站以来，研究人员同时使用了机械温湿记录仪及配套记录图纸，以及搭载电子数据记录仪的温度传感器来测量并记录气温。因此，若要构建高质量的萨德尔站每日气温时间序列，需仔细排查仪器更替带来的潜在影响，并参考研究人员留存的相关记录。
本数据集提供了经过质量控制、数据插补后的每日气温时间序列，涵盖最高气温、平均气温、最低气温与气温日较差，并考量了萨德尔站的仪器更替情况。数据插补方法沿用了尼沃特岭长期生态研究站点D1与C1站的长期每日气温插补方案，以保证核心馆藏每日气温数据集的一致性。本数据包的元数据集中收录了萨德尔站气温观测最完整的站点历史记录，并为数据使用者提供了在科学分析中使用该数据集时需关注的相关说明与局限性提示。