Comparison Study of Upper Stratosphere and Lower Mesosphere Temperature Climatology Over Beijing (40.5°N, 116.2°E) and Haikou (19.9°N, 110.3°E), China With Rayleigh Lidar and TIMED/SABER Measurements

The observation and study of middle atmospheric temperatures play a crucial role in understanding various complex dynamical and radiative processes. Based on Rayleigh lidar measurements from Beijing (40.5°N, 116.2°E) and Haikou (19.9°N, 110.3°E) in 2022 and 2023, over a total of 249 and 139 nights comprising 2,237 and 1,276 hr, respectively, this study analyzes and compares the atmospheric temperature variation characteristics between 30 and 60 km in the middle and low latitudes. The results reveal significant differences in temperature variations between the two locations. The monthly mean stratopause temperature over Beijing varies between 253 and 267 K, exhibiting an annual oscillation (AO). In contrast, the stratopause temperature over Haikou varies between 263 and 273 K, showing a semi-annual oscillation (SAO). The temperatures are used to derive the seasonal variation of lapse rate ($-\partial \bar{T}/\partial z$) and the buoyancy frequency square ($N^2$). The lapse rate and $N^2$ in both locations exhibit an annual oscillation, with summer extrema in the upper stratosphere and lower mesosphere. Beijing has greater stability in the lower mesosphere, while Haikou shows higher stability in the upper stratosphere. Using the SABER kinetic temperature data set from 2023, which spans 50°S–50°N and 180°W–180°E, it was found that the boundary between AO and SAO in stratopause temperature is located around 28°N and 18°S, respectively, highlighting an asymmetric structure between the Northern and Southern Hemispheres, which is potentially driven by the stronger intensity of AO in the Southern Hemisphere. This work enhances the understanding of the relationship between the seasonal variations of stratopause temperature and geographical latitude.