Meteor radar data collected over Langfang, China (39.4° N, 116.7° E) were used to estimate the momentum flux of short-period (less than 2 h) gravity waves (GWs) in the mesosphere and lower thermosphere (MLT), using the Hocking (2005) analysis technique. Seasonal variations in GW momentum flux exhibited annual oscillation (AO), semiannual oscillation (SAO), and quasi-4-month oscillation. Quantitative estimations of GW forcing toward the mean zonal flow were provided using the determined GW momentum flux. The mean flow acceleration estimated from the divergence of this flux was compared with the observed acceleration of zonal winds displaying SAO and quasi-4-month oscillations. These comparisons were used to analyze the contribution of zonal momentum fluxes of SAO and quasi-4-month oscillations to zonal winds. The estimated acceleration from high-frequency GWs was in the same direction as the observed acceleration of zonal winds for quasi-4-month oscillation winds, with GWs contributing more than 69%. The estimated acceleration due to Coriolis forces to the zonal wind was studied; the findings were opposite to the estimated acceleration of high-frequency GWs for quasi-4-month oscillation winds. The significance of this study lies in estimating and quantifying the contribution of the GW momentum fluxes to zonal winds with quasi-4-month periods over mid-latitude regions for the first time.

We conducted meteor observations during the Leonid meteor shower on 16 November 2017 and 17 November 2018 with Langfang medium frequency (MF) radar (116° E, 40° N). This was the first nighttime meteor observation by MF radar in mid-latitude China. The observation period was 12:00–22:00 (UT) and the observation range was 78–150 km. By using broad vertical beams, totally 94 and 92 meteor echoes were obtained, along with their spatial, time and height distribution. Quite a few meteor echoes are within 30° zenith angles, from the southwest direction, and with a mean height of 107 km which is almost 10 km higher than traditional VHF (Very High Frequency) meteor radar observations. Initial bi-hourly and nightly averaged wind profiles were calculated, and well fitted the wind estimations by co-located VHF meteor radar at the altitude of 100–110 km. On the other side, echoes around 140 km are successfully detected in our observation, which may suggest that for most running MF radars, meteor echoes around 140 km altitude could be detected with a sampling pulse frequency less than 100 Hz.

Summertime westward-to-eastward zonal wind reversal near the mesopause is a key manifestation of wave–mean flow interaction in the mesosphere and lower thermosphere. We examined this zonal wind reversal over Langfang, China, during May–July 2024 using co-located MF and meteor–radar winds together with SD-WACCM output. The reversal height and vertical shear near the reversal height were obtained from a linear fitting. Both radars showed pronounced temporal dependence for the zonal wind-reversal height, with a higher height at the beginning of summer, which decreased from May to July. The MF radar placed the transition slightly higher than meteor radar, both of which are confined to the mesopause region. The SD-WACCM output showed clear zonal wind reversal, but the reversal heights were between MF and meteor observations. Moreover, the decreasing trend of the zonal wind-reversal height in the SD-WACCM output was less evident than in radar observations. Nevertheless, the zonal wind reversal exhibited clear diurnal variations. The total zonal wind tendency due to gravity wave-breaking in the SD-WACCM output was utilized to diagnostically analyze the reasons, wherein diurnal variations in the wind-reversal height corresponded well to the diurnal variations in gravity wave-dragging. Monthly model diagnostics further showed the positive strengthening of gravity wave drag near 80–90 km from May to July. Our analysis showed that the temporal variation in the background flow and the reversal layers during 2024 were intimately related to gravity wave momentum deposition locally and globally.

中频雷达用来开展夜间100km高度以上的流星观测，获得流星随时间、高度、方位的分布情况及流星体速度、流星辐射点、流星余迹径向速度等参数，其探测数据可用于流星天文学、中层大气动力学等领域的研究.利用2017年11月16日12：00UT-22：00UT期间廊坊观测站（39.4°N，116.7°E）的中频雷达数据，首次开展了中国中纬度地区夜间流星观测实验，共检测到94个流星回波信号，集中分布在97～115km高度范围内，平均高度为106.5km，计算得到了流星回波的双极扩散系数、方位分布等相关参数，并与国外中频雷达流星探测结果进行了初步比较.