El Niño has an important influence on climate systems. There are obviously negative water vapor anomalies from radiosonde observations in the tropical western Pacific during El Niño. The tropical Hadley, Walker, and monsoon circulation variations are revealed to play different roles in the observed water vapor anomaly in different types of El Niños. The Walker (monsoon) circulation anomaly made a major contribution in the 2015/16 (2009/10) strong eastern Pacific (central Pacific) El Niño event.

Using the Beijing MST radar echo-power observations collected during the period November 2011–May 2017, the structure and variability of the tropopause over Xianghe, China (39.75° N, 116.96° E), was presented. Our comparison results showed a good agreement between the radar and thermal tropopauses during all seasons. In contrast, the consistency between the radar and dynamical tropopauses is poor during summer. Diurnal oscillation in tropopause height is commonly observed during all seasons.

Turbulence dissipation rate has inter-annual variations and follows a lognormal distribution. The magnitudes of turbulence detected by radiosonde and radar are roughly comparable. Turbulence cannot predicted by instabilities well but trends to be vigorous under the instability condition. The propagating gravity waves in the lower atmosphere can enhance atmospheric instabilities, and the temporal variations of waves can roughly estimate the turbulence dissipation rate at different height.

Downward stratospheric intrusions are well known as an important source of tropospheric ozone. In the light of the present understanding, several unanswered questions remain regarding the use of VHF radars to identify stratospheric intrusions. Our study found that the radar-observed strong downdrafts preceding the rapid tropopause ascent are a strong diagnostic for possible intrusions. This will have important implications for air-quality monitoring and long-term estimation of troposphere ozone.

We present the first statistical results of vertical wind fluctuation spectra, which revealed a very shallow spectral structure, with mean slopes of −0.58 and −0.23 in the troposphere and lower stratosphere, respectively. No existing spectral theories can comprehensively explain the observed three-dimensional wind spectra, indicating that the spectral features of atmospheric fluctuations are far from fully understood.

The 6.5-day traveling planetary wave is able to impact the ionosphere/thermosphere via a dissipation mechanism. Ionospheric TEC and thermosphere O/N2 exhibit an apparent decrease as the result of extra meridional circulation induced by 6.5-day wave dissipation. Our work suggests that the modulation of E-dynamo is not the unique pathway through which planetary waves substantially influence the IT system.