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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).