Impact of natural variability in the 11-year mesopause region temperature observation over Fort Collins, CO (41°N, 105°W) Original Research Article

The Colorado State University Sodium Lidar has measured temperatures in the mesopause region (80–105 km) for over 11 years. Based on 7 yearsʹ observation, an episodic change with a warming of 11.8 K in 1993 at the mean mesopause altitude of 98 km, attributable to Mt. Pinatubo eruptions, was reported. In this paper, we focus on the solar cycle effects. With 11 years of data, we observed a maximum solar response of 0.06 K/SFU at 99 km, which decreases at lower and higher altitudes to nearly zero and appears to change sign at ∼82 and ∼104 km. The phase changes are consistent with earlier midlatitude observation with incoherent scatter radar above and Rayleigh lidar below the altitudes reported here, providing clear experimental evidence of dynamical influences throughout different layers of Earthʹs atmosphere. We discuss the altitude dependence of response amplitudes and the effect of volcanic and solar flux variability have on the mesopause region temperatures, as well as long-term temperature trends.