Seasonal oscillations of middle atmosphere temperature observed by Rayleigh lidars and their comparisons with TIMED/SABER observations

The long-term temperature data sets obtained by Rayleigh lidars at six different locations from low to high latitudes within the Network for the Detection of Atmospheric Composition Change (NDACC) were used to derive the annual oscillations (AO) and semiannual oscillations (SAO) of middle atmosphere temperature: Reunion Island (21.8°S); Mauna Loa Observatory, Hawaii (19.5°N); Table Mountain Facility, California (34.4°N); Observatoire de Haute Provence, France (43.9°N); Hohenpeissenberg, Germany (47.8°N); Sondre Stromfjord, Greenland (67.0°N). The results were compared with those derived from the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument onboard the Thermosphere-Ionosphere-Mesosphere Energetics and Dynamics (TIMED) satellite. The zonal mean temperatures at similar latitudes show good agreement. The observations also reveal that the AO dominates the seasonal oscillations in both the stratosphere and the mesosphere at middle and high latitudes, with the amplitudes increasing poleward. The SAO oscillations are weaker at all six sites. The oscillations in the upper mesosphere are usually stronger than those in the upper stratosphere with a local minimum near 50-65 km. The upper mesospheric signals are clearly out of phase with upper stratospheric signals. Some differences between lidar and SABER results were found in both the stratosphere and mesosphere. These could be due to: the difference in data sampling between ground-based and space-based instruments, the length of data set, the tidal aliasing owing to the temperature AO and SAO since lidar data are nighttime only, and lidar temperature analysis algorithms. The seasonal oscillations of tidal amplitudes derived from SABER observations suggests that the tidal aliasing of the lidar temperature AO and SAO in the upper mesosphere may over- or under-estimate the real temperature oscillations, depending on the tidal phases. In addition, the possibly unrealistic seasonal oscillations embedded in the climatological models (e.g., MSIS or CIRA) at the reference point for lidar temperature analysis may also affect the lidar results in the top part of the profiles (usually in the upper mesosphere).