Recent research progress on planetary waves in the middle and upper atmosphere during sudden stratospheric warmings

Sudden stratospheric warming (SSW) is a violent atmospheric disturbance in the polar region of the winter hemisphere. The drastic changes in temperature and wind during SSWs are considered to be the main reasons for the abnormal increase in the energy of atmospheric waves in the upper and middle atmosphere in the winter hemisphere. Meteor radar is an important ground-based detection equipment that can stably and continuously detect neutral wind in the mesosphere and lower thermosphere (MLT) region. Based on one of the National Major Science Infrastructure Projects, the "Meridian Project", China has built several meteor radar observation stations to conduct long-term stable and continuous monitoring of the neutral wind in the MLT region, which provides important observation data for revealing the physical mechanism of abnormal changes in atmospheric waves during SSWs. Here, we briefly review the research progress on planetary waves in the middle and upper atmosphere during SSWs in recent years, especially the scientific findings based on the meteor radars in the Chinese "Meridian Project". The trigger mechanisms of the enhanced planetary waves during SSWs are discussed. With the completion of ten meteor radars in the second phase of the "Meridian Project", this paper prospects the use of its meteor radar monitoring network to further study the characteristics of atmospheric waves in the middle and upper atmosphere during SSWs.