Westward Acceleration of Tropical Stratopause Zonal Winds During Major Sudden Stratospheric Warming Events

The tropical Mesosphere‐Lower Thermosphere‐Ionosphere system is found to show significant variabilities during Sudden Stratospheric Warming (SSW) events. Recent studies have highlighted the possible role played by modified background wind conditions in communicating the SSW‐induced stratospheric perturbations to the Mesosphere‐Lower Thermosphere‐Ionosphere region. In the present study, changes in the background zonal winds at the tropical stratopause during major SSW events inferred from MERRA‐2 reanalysis data sets, rocket observations, and model simulations are reported for the first time. The tropical stratopause shows enhanced westward winds during the course of major SSW events. Rocketsonde observations from a low latitude station Thumba (8.5 ° N,76.9 ° E) also showed significant westward acceleration during three major SSW events. Further, Specified Dynamics version of the Whole Atmosphere Community Climate Model simulations for the 2008–2009 SSW replicate the observed features. Plain Language Summary The winter time polar stratosphere undergoes sudden reversal of climatological eastward winds to westward winds accompanied by a large increase in temperature during dramatic events called Sudden Stratospheric Warmings. Previous studies have shown that the upper atmosphere (Thermosphere/Ionosphere) over low latitudes show strong signatures associated with these polar phenomena. Changes in the tropical middle atmospheric background winds in response to Sudden Stratospheric Warming events are thought to have a significant role in causing the observed changes in the upper atmosphere. In the current study, abrupt changes in stratopause winds over the low latitudes are reported using reanalysis, observations, and model simulations. Present results can contribute to understanding several features observed in the low latitude upper atmospheric altitudes in connection with these polar sudden warming episodes. Key Points Enhanced westward winds at the tropical stratopause during major Sudden Stratospheric Warming (SSW) events in the Northern Hemisphere Westward acceleration of stratospheric winds during both split and displacement type SSW events Poleward shift of the tropical zero wind line during the course of the warming