Comment on egusphere-2022-998

Abstract

The Madden–Julian oscillation (MJO) is the dominant mode of intraseasonal variability in the troposphere. The influence of the MJO on the middle atmosphere (MA) and particularly on its temperature is of interest for both the understanding of MJO-induced teleconnections and research on the variability of the middle atmosphere. However, only few studies dealing with the influence of the MJO on MA temperature are available. We analyze statistically the connection of the MJO and the MA zonal mean temperature based on observations by the MLS satellite instrument. We consider all eight MJO phases, different seasons and the state of the quasi-biennial oscillation (QBO). We show that the MA temperature is influenced by the state of MJO in large areas of the MA and under roughly all considered atmospheric conditions. The zonal mean temperature response is characterized by a particular spatial pattern, which we link to the interhemispheric coupling (IHC) mechanism, a known dynamical feature of the MA. The strongest temperature deviations are on the order of ± 10 K and are found in the polar winter MA during boreal winter when the QBO is in the easterly phase. Other atmospheric conditions also show temperature responses with the characteristic spatial pattern, but weaker and more noisy. The QBO turns out to have a relatively big influence during boreal winter but only a small influence during austral winter. We also discuss the role of sudden stratospheric warmings (SSWs), which have an ambivalent influence on our interpretation, because they introduce strong temperature variability in the polar winter MA themselves. In addition, SSWs are one possibility to explain the QBO influence during boreal winter. Furthermore, we also analyze the change of the temperature response pattern while the MJO progresses from one phase to the next. We find a largely systematic reaction of the MA to the phase changes, particularly a gradual altitude shift of the MA temperature response pattern, which can be seen more or less clearly depending on the atmospheric conditions. Overall, a major outcome of the present study is the finding that the tropospheric MJO can trigger the IHC mechanism, which affects many areas of the MA. It is therefore a noteworthy example for the complex couplings across different atmospheric layers and geographical regions in the atmosphere. Additionally, it highlights close linkages of known dynamical features of the atmosphere, particularly the MJO, the IHC, the QBO, and SSWs. Because of the wide coverage of atmospheric regions and included dynamical features, the results might help to further constrain the underlying dynamical mechanisms and could be used as a benchmark for the representation of atmospheric couplings on the intraseasonal timescale in atmospheric models.