Abstract Based on the round-trip intelligent sounding system, we used the structure function and spectrum analysis method to analyze the interaction between the small-scale gravity wave and turbulence in the middle stratosphere. The result showed that the generation of turbulence was closely related to the Kelvin-Helmholtz(KH) billows. An upscale energy cascade occurred on the spatial scale of KH billows, while a downscale energy cascade occurred on a larger spatial scale (gravity wave scale), which resulted in the breaking of the gravity wave and turbulence. Obvious two-dimensional turbulence that the inverse energy cascade in 2D exists simultaneously with a direct enstrophy cascade to the small scales was found, which is considered to be the first-hand observation result of relevant height.

Based on the round-trip intelligent sounding system, we used the structure function and spectrum analysis method to analyze the interaction between the small-scale gravity wave and turbulence in the middle stratosphere. The result showed that the generation of turbulence was closely related to the Kelvin-Helmholtz(KH) billows. An upscale energy cascade occurred on the spatial scale of KH billows, while a downscale energy cascade occurred on a larger spatial scale (gravity wave scale), which resulted in the breaking of the gravity wave and turbulence. Obvious two-dimensional turbulence that the inverse energy cascade in 2D exists simultaneously with a direct enstrophy cascade to the small scales was found, which is considered to be the first-hand observation result of relevant height.

The global distribution and variations of the monthly mesopause temperature are presented during 2002-2019 covering the latitudes of 83°S-83°N based on Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) observations. To investigate the long-term trend and solar response of the mesopause temperature, a three-component harmonic fit is first applied to remove the seasonal variation from the monthly temperature data series. Then a multiple linear regression model is performed to residual temperatures versus constant, time series, solar activity, and geomagnetic activity terms. In this study, the mesopause temperature shows a cooling trend through all latitudes ranging from -0.002 to -0.113 K/year with a mean of -0.069 ± 0.036 K/year. The cooling trends in the southern hemisphere are observed to be relatively stronger than those in the northern hemisphere. For high latitudes (60°– 80°), significant negative trends can be detected during the non-summer time, while no significant trends are found for summertime. The mesopause temperature shows apparent positive responses to solar activity through all latitudes ranging from 2.74 to 4.76 K/100sfu with a mean of 3.94 ± 0.59 K/100sfu, which are more significant and stable in the northern hemisphere. There is a pronounced drop in solar response near the equator, which could be caused by tidal forcing at low latitudes. It is noteworthy that the length of the time interval for analysis is the main factor influencing the quality of the results. Our results, using an eighteen years interval, are expected to be a robust reference for the mesopause temperature variations.