Unusual Mesospheric Zonal Wind Reversal Observed by the Wuhan MST Radar During the Winter 2015/2016

Abstract

An unusual zonal wind reversal unrelated to Sudden Stratospheric Warming events in the mesosphere is detected by the Wuhan MST radar (29.51°N, 114.13°E) during the winter of 2015/2016. Interestingly, an upper stratosphere/lower mesosphere (USLM) disturbance is captured at the beginning of the wind reversal. We find this abnormal zonal wind reversal is related to the enhanced activity of PW2 in the mesosphere by using Modern-Era Retrospective Analysis for Research and Applications version 2 reanalysis data. Further diagnostic analysis suggests that the enhanced planetary waves (PWs) may have developed from the broken PWs during the USLM. Simultaneously, the mesosphere of 30°–40°N contains additional wave sources associated with the baroclinic/barotropic instability. These enhanced PWs eventually cause the wind reversal. Additionally, during the wind reversal, the radar is in the position of constant negative temperature gradient and colder region, favoring the continuation of the wind reversal.