Analysis of the correlation between horizontal wind and 11‐year solar activity over Langfang, China

In this study, long term observations of medium frequency (MF) radar at Langfang site (39.4°N, 116.7°E) from 2009 to 2020 have been used to analyze the dependence of the 11‐year solar cycle on horizontal winds in the local mesosphere and lower thermosphere (MLT). The results show that the zonal wind is positively correlated with solar activity during spring at 80–84 km, and during summer at 80–82 km; the meridional wind is positively correlated with solar activity during spring at 84–88 km and during summer at 84–90 km. In contrast, the results show no correlation between the horizontal wind and solar activity in autumn and winter. We attempt to explain the correlations in terms of the changes in stratospheric temperature and the net flux of gravity waves during solar activities. In addition, annual and semiannual oscillations of the zonal/meridional wind were found by using the least squares fitting method on daily horizontal winds, which show negative correlations with solar activity at heights of 80–90 km. Key Points The responses of atmospheric horizontal wind and tides at the height of 80–100 km to 11‐year solar activities are analysed. The zonal/meridional wind is positively correlated with solar activities in spring and summer, and the amplitude of annual and semiannual oscillations of the zonal/meridional wind is mainly negatively correlated with solar activities. A mechanism is proposed that the solar activities could affect the stratospheric thermal and wind structure, leading to change of upward propagating gravity wave net flux, and finally affect the MLT atmospheric wind field.