Impact of a strong volcanic eruption on the summer middle atmosphere in UA-ICON simulations

Abstract

Abstract. Explosive volcanic eruptions emitting large amounts of sulfur can alter the temperature of the lower stratosphere and change the circulation of the middle atmosphere. The dynamical response of the stratosphere to strong volcanic eruptions has been the subject of numerous studies. The impact of volcanic eruptions on the mesosphere is less well understood because of a lack of large eruptions in the satellite era and only sparse observations before that period. Nevertheless, some measurements indicated an increase in mesospheric mid-latitude temperatures after the 1991 Pinatubo eruption. The aim of this study is to uncover potential dynamical mechanisms that may lead to such a mesospheric temperature response. We use the upper-atmospheric icosahedral non-hydrostatic (UA-ICON) model to simulate the atmospheric response to an idealized strong volcanic injection of 20 Tg S into the stratosphere (about twice as much as the eminent 1991 Pinatubo eruption). The simulation shows a significant warming of the polar summer mesospause of up to 15–21~K in the first November after the eruption. We argue that this is mainly due to intrahemispheric dynamical coupling in the summer hemisphere and potentially enhanced by interhemispheric coupling with the winter stratosphere. This study will focus on the first austral summer after the eruption, because mesospheric temperature anomalies are especially relevant for the properties of noctilucent clouds whose season peaks around January in the southern hemisphere.

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

“…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).…”

“…It has also been suggested that part of the apparent 11-year solar signature in PMCs in the SBUV record before 2000 may be caused indirectly by the eruptions of the volcanoes El Chichón in 1982 and Mount Pinatubo in 1991 (Hervig et al, 2016). The underlying physical mechanisms are not well understood, and may also involve intra-and inter-hemispheric coupling via gravity waves (Wallis et al, 2023).…”

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

“…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). It is important to note that the underlying mechanisms are not fully understood for the latter two examples.…”

“…It has also been suggested that part of the apparent 11-year solar signature in PMCs in the SBUV record before 2000 may be caused indirectly by the eruptions of the volcanoes of El Chichón in 1982 and Mount Pinatubo in 1991 (Hervig et al, 2016). The underlying physical mechanisms are not well understood and may also involve intra-and interhemispheric coupling via gravity waves (Wallis et al, 2023).…”