Simultaneous Rayleigh-Scatter and Sodium Resonance Lidar Temperature Comparisons in the Mesosphere-Lower Thermosphere

The Utah State University (USU) campus (41.7 degrees N, 111.8 degrees W) hosts a unique upper atmospheric observatory that houses both a high-power, large-aperture Rayleigh lidar and a Na lidar. For the first time, we will present 19 nights of coordinated temperature measurements from the two lidars, overlapping in the 80-110km observational range, over one annual cycle (summer 2014 to summer 2015). This overlap has been achieved through upgrades to the existing USU Rayleigh lidar that increased its observational altitude from 45-95 to 70-115km and by relocating the Colorado State Na lidar to the USU campus. Previous climatological comparisons between Rayleigh and Na lidar temperatures have suggested that significant temperature differences exist between the two techniques. This new comparison aims to further these previous studies by using simultaneous, common-volume observations. The present comparison showed the best agreement between 85 and 95km, with a temperature difference, averaged over the whole data set, of about 1.10.5K. Larger differences occurred above and below these altitudes with the Rayleigh temperatures being colder by about 3.50.5K at 82km and warmer by up to 9.13.5K above 95km.