Responses of zonal wind at ∼40° N to stratospheric sudden warming events in the stratosphere, mesosphere and lower thermosphere

Based on the data at similar to 40 degrees N at different longitudes during different stratospheric sudden warming (SSW) events, the responses of zonal winds in the stratosphere, mesosphere and lower thermosphere to SSWs are studied in this paper. The variations of zonal wind over Langfang, China (39.4 degrees N, 116.7 degrees E) by MF radar and the modern era retrospective-analysis for research and applications (MERRA) wind data during 2010 and 2013 SSW and over Fort Collins, USA (41 degrees N, 105 degrees W) by lidar and MERRA wind data during 2009 SSW are compared. Results show that the zonal wind at similar to 40 degrees N indeed respond to the SSWs while different specifics are found in different SSW events or at different locations. The zonal wind has significant anomalies during the SSWs. Over Langfang, before the onset of 2010 and 2013 SSW, the zonal wind reverses from eastward to westward below about 60-70 km and accelerates above this region, while westward wind prevails from 30 to 100 km after the onset of 2010 SSW, and westward wind prevails in 30-60 and 85-100 km and eastward wind prevails in 60-85 km after the onset of 2013 SSW. Over Fort Collins during 2009 SSW, eastward wind reverses to westward in 20-30 km before the onset while westward wind prevails in 20-30 and 60-97 km and eastward wind prevails in 30-60 and in 97-100 km after the onset. Moreover, simulations by the specified dynamics version of the whole atmosphere community climate model (SD-WACCM) are taken to explain different responding specifics of zonal wind to SSW events. It is found that the modulation of planetary wave (PW) plays the main role. Different phases of PWs would lead to the different zonal wind along with longitudes and the different amplitudes and phases in different SSW events can lead to the different zonal wind responses.