Mesopause temperatures and relative densities at midlatitudes observed by the Mengcheng meteor radar

The atmospheric temperatures and densities in the mesosphere and lower thermosphere (MLT) region are essential for studying the dynamics and climate of the middle and upper atmosphere. In this study, we present more than 9 years of mesopause temperatures and relative densities estimated by using ambipolar diffusion coefficient measurements observed by the Mengcheng meteor radar (33.4 degrees N, 116.5 degrees E). The intercomparison between the meteor radar and Thermosphere Ionosphere Mesosphere Energetics and Dynamics/Sounding of the Atmosphere by Broadband Emission Radiometry (TIMED/SABER) and Earth Observing System (EOS) Aura/ Microwave Limb Sounder (MLS) observations indicates that the meteor radar temperatures and densities agree well with the simultaneous satellite measurements. Annual variations dominate the mesopause temperatures, with the maximum during winter and the minimum during summer. The mesopause relative densities also show annual variations, with strong maxima near the spring equinox and weak maxima before the winter solstice, and with a minimum during summer. In addition, the mesopause density exhibits a structure similar to that of the zonal wind: as the zonal wind flows eastward (westward), the mesopause density decreases (increases). At the same time, the meridional wind shows a structure similar to that of the mesopause temperature: as the meridional wind shows northward (southward) enhancements, the mesopause temperature increases (decreases). Simultaneous horizontal wind, temperature, and density observations provide multiple mesospheric parameters for investigating mesospheric dynamics and thermodynamic processes and have the potential to improve widely used empirical atmospheric models.