Infilled daily air temperature data for C1 chart recorder, 1952 - ongoing.

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).