The first near year-round Rayleigh Lidar temperature and wave activity measurements of the Arctic upper stratosphere and lower mesosphere are presented. The data were obtained from Sondrestrom, Greenland (67° N, 51° W) throughout 1995-1998. The relatively continuous, high frequency measurements of vertical thermal profiles, root-mean-square (RMS) atmospheric relative-density perturbations, and their associated variability over the four years at one geographic site complement previously published Arctic climatologies that were based on various mixed data sets. The nightly, monthly, and yearly variability of the values was seen to be much larger in the winter periods than in the surnmer. This is attributed to both the strong influence of the polar vortex and its associated variability as well as the increased potential for atmospheric wave activity in the middle atmosphere during these periods. Winter temperatures from empirical models resemble measured temperatures only after a long-term average of the observations, suggesting constraints/limitations on both short term observations as well as model comparisons/applications. Model temperatures more closely and consistently resemble observed temperatures obtained from late spring through late fall. RMS values display a strong annual trend, with a maximum in the winter and a minimum in the summer. The need for estimates of geophysical variability in both model outputs and model/data comparisons, as well as the need for multi-site observations, is also discussed.