Signatures of the Madden-Julian Oscillation in Middle Atmosphere zonal mean Temperature: Triggering the Interhemispheric Coupling pattern

Abstract

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.

Opinion: Recent developments and future directions in studying the mesosphere and lower thermosphere

“…Garfinkel et al, 2012;Yang et al, 2019). As noted previously, the recent study by Hoffmann et al (2022) suggests that the MLT region is also affected by the MJO via the interhemispheric coupling mechanism.…”

“…The interhemispheric coupling phenomenon is particularly relevant for the variability in the NLCs or PMCs in the polar summer mesopause, and this has been used in several pioneering studies (Gumbel and Karlsson, 2011;Karlsson et al, 2007). The typical interhemispheric coupling pattern in the middle-atmospheric temperature field may be triggered by altered planetary wave activity and/or stratospheric warmings and has also recently been proposed to be present in observational data in the context of a possible Madden-Julian oscillation (MJO) signature in the middle atmosphere (Hoffmann et al, 2022). In addition, it has been suggested that the thermodynamical effects of volcanic eruptions may affect the interhemispheric coupling pattern (Wallis et al, 2023).…”

Opinion: Recent Developments and Future Directions in Studying the Chemistry of the Mesosphere and Lower Thermosphere

“…Garfinkel et al (2012); Yang et al (2019)). The recent study by Hoffmann et al (2022) suggests that the MLT region is also affected by the MJO via the interhemispheric coupling mechanism.…”

“…The interhemispheric coupling phenomenon is particularly relevant for the variability of NLC/PMCs in the polar summer mesopause and this has been used in several pioneering studies (Gumbel and Karlsson, 2011;Karlsson et al, 2007). The typical interhemispheric coupling pattern in the middle atmospheric temperature field may be triggered by altered planetary wave activity and/or stratospheric warmings, and has also recently been identified in experimental data in the context of a possible Madden-Julian-Oscillation (MJO) signature in the middle atmosphere (Hoffmann et al, 2022). In addition, the dynamical/thermal effects of volcanic eruptions may impact on the interhemispheric coupling pattern (Wallis et al, 2023).…”