Dynamical influence of the Madden-Julian oscillation on the Northern Hemisphere mesosphere during the boreal winter

This study first investigates the effect of the Madden-Julian Oscillation (MJO) on the Northern Hemisphere (NH) mesosphere. Both observations and simulations suggest significant cooling in the NH polar mesosphere approximately 35 days after MJO phase 4 (P4), which lags the MJO-induced perturbation in the upper stratosphere by 10 days. The enhanced planetary waves (PWs) propagate upward and result in wavenumber-1 pattern temperature anomalies in the mesosphere lagging MJO P4 by 25 days. The anomalous PWs also lead to the weaker eastward zonal wind in the upper stratosphere and lower mesosphere lagging MJO P4 by 30 days. Simultaneously, the weaker westerlies result in weaker climatological westward gravity waves (GWs) in the mesosphere due to critical-level filtering. The mesosphere meridional circulation is suppressed due to both anomalous PWs and GWs, and this suppression causes polar mesospheric cooling lagging MJO P4 by 35 days.