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Climatological data were collected from a Niwot Ridge climate station (D1) throughout the year. From July 5 2000 through October 23 2013, data were recorded using a Campbell Instruments CR23X data logger. Subsequently, data were recorded using a Campbell Instruments CR1000 data logger. Maximum and minimum values are recorded instantaneously, with a sampling interval of 5 seconds. Daily averages and totals were calculated from 17,280 individual measurements. This instrument was programmed to generate both hourly and daily output. Beginning in June 25 2009, 10 minute output was also generated. Daily output generated by the logger ended in 2014. Beginning in 2014, daily values were calculated from the native resolution data (ten minute). 

Climatological data were collected from the saddle climate station on Niwot Ridge (3525 m elevation) throughout the year. From 2000-06-24 to 2012-03-24, data were recorded using a Campbell Instruments CR23X data logger. Subsequently, data were recorded using a Campbell Instruments CR1000 data logger. Maximum and minimum values were recorded instantaneously, with a sampling interval of 5 seconds. Daily means and totals were calculated from 17,280 individual measurements. The CR23X logger was programmed to generate both hourly and daily output. The CR1000 logger generated daily, hourly, and minute data until September 2014, and 10 minute and minute data thereafter. 

Climatological data were collected from the saddle climate station on Niwot Ridge (3525 m elevation) throughout the year. From 2000-06-24 to 2012-03-24, data were recorded using a Campbell Instruments CR23X data logger. Subsequently, data were recorded using a Campbell Instruments CR1000 data logger. This data set includes data beginning in 2009. Maximum and minimum values were recorded instantaneously, with a sampling interval of 5 seconds. Hourly means and totals were calculated from 720 individual measurements. The CR23X logger was programmed to generate both hourly and daily output. The CR1000 logger generated daily, hourly, and minute data until September 2014, and 10 minute and minute data thereafter. This dataset discontinued, see methods for instructions on accessing the 10 minute data instead. 

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. 

As part of its long-term climate data core collection, the Niwot Ridge LTER has collected daily precipitation 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. Here we present a quality-controlled, gap-filled, daily precipitation time series corrected for blowing snow overcatch at the Saddle station. Methods follow those used to gap-fill long-term daily precipitation at the Niwot Ridge LTER D1 and C1 stations so there is consistency among core collection daily precipitation datasets. Metadata for this data package centralizes the most complete station history for Saddle precipitation and includes notes to data users on aspects and limitations of the dataset to consider when using these data in scientific analyses. Because of unresolved data quality concerns with winter precipitation the first several years of the record, gap-filled data for winter months (October–May) 1981-10-01 through 1987-05-30 are removed. 

Precipitation data have been collected at the C1 climate station (3022 m asl) almost continuously from 1952 to the present. C1 is on locally level terrain on the southeastern flank of Niwot Ridge, 9.7 km east of the Continental Divide. Surrounding vegetation is closed-canopy subalpine conifer forest. Through 1964, precipitation was recorded using an unshielded U.S. Weather Bureau standard totalizing gauge, with observations manually recorded on an approximately weekly basis. The gauge was located in an open area with sparse tree cover adjacent to the forest proper. Starting in late 1961, daily precipitation has been recorded using a Belfort Universal weighing-bucket gauge with chart recorder in an 8-m diameter clearing in the forest; the forest provides natural shielding for the gauge. The two records were assessed for an impact of this station change on record homogeneity and merged (see Methods). Missing daily data were infilled and multiday records were parsed to dailies (see Methods). 

Precipitation data have been collected at the D1 climate station (3739 m asl) almost continuously from 1952 to the present. D1 is on a narrow, exposed ridge on the westernmost part of Niwot Ridge, 2.6 km east of and ca. 200 m lower in elevation than the Continental Divide. Surrounding vegetation is low-stature alpine tundra. Through 1969, precipitation was recorded using an unshielded U.S. Weather Bureau standard totalizing gauge, with observations manually recorded on an approximately weekly basis. Starting in 1965, daily precipitation has been recorded using a Belford weighing-bucket gauge with chart recorder and with an Alter-type shield encircled by a Wyoming-snow fence. Overlap in the two records was used to adjust the totalizing gauge record so that it could be merged with the weighing-bucket gauge record (see Methods). Missing daily data were infilled and multiday records were parsed to dailies (see Methods). 

Daily minimum and maximum surface air temperature data have been collected at the C1 climate station (3022 m asl) almost continuously from 1952 to the present. C1 is on locally level terrain on the southeastern flank of Niwot Ridge, 9.7 km east of the Continental Divide. Surrounding vegetation is generally closed-canopy subalpine conifer forest. Temperature minima and maxima were measured with a chart-recording hygrothermograph housed in a Stevenson screen located in an open, sparsely treed area adjacent to the forest proper. Hygrothermograph records were calibrated at the time of chart changes against liquid-in-glass thermometers. Processing included quality checks and infilling of missing daily data (see Methods). 

Daily minimum and maximum surface air temperature data have been collected at the D1 climate station (3739 m asl) almost continuously from 1952 to the present. D1 is on a narrow, exposed ridge on the westernmost part of Niwot Ridge, 2.6 km east of and ca. 200 m lower in elevation than the Continental Divide. Surrounding vegetation is low-stature alpine tundra. Temperature minima and maxima were measured with a chart-recording hygrothermograph housed in a Stevenson screen. Hygrothermograph records were calibrated at the time of chart changes against liquid-in-glass thermometers. Processing included quality checks and infilling of missing daily data (see Methods). 

Temperature data were collected on a daily time-scale from the C1 climate station (3018 m) since 1952. Over time various circumstances have led to days with missing values. Some missing values were estimated from redundant sensors and nearby climate stations using various methods. Greenland 1987 was a basis for the methodology. However when it was not possible to use this methodology, new methods were developed.