Climatology and Forcing of the Quasi-Biennial Oscillation in the MAECHAM5 Model

Giorgetta, Marco; Manzini, Elisa; Roeckner, Erich; Esch, Monika; Bengtsson, Lennart

doi:10.1175/jcli3830.1

Cited by 239 publications

(292 citation statements)

References 32 publications

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“…The simulations for this study were performed with the middle atmosphere version of the general circulation model (GCM) ECHAM5 (Giorgetta et al, 2006), using the spectral truncation at wave-number 42 (T42) and 90 vertical layers up to 0.01 hPa. The GCM solves prognostic equations for temperature, surface pressure, vorticity, divergence, and phases of water.…”

Section: Model Setupmentioning

confidence: 99%

“…The GCM solves prognostic equations for temperature, surface pressure, vorticity, divergence, and phases of water. In this model version with 90 vertical levels the quasi-biennial oscillation (QBO) in the tropical stratosphere is internally generated (Giorgetta et al, 2006). The aerosol microphysical model HAM (Stier et al, 2005) is interactively coupled to the GCM.…”

Section: Model Setupmentioning

confidence: 99%

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Changing transport processes in the stratosphere by radiative heating of sulfate aerosols

2017

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Abstract. The injection of sulfur dioxide (SO 2 ) into the stratosphere to form an artificial stratospheric aerosol layer is discussed as an option for solar radiation management. Sulfate aerosol scatters solar radiation and absorbs infrared radiation, which warms the stratospheric sulfur layer. Simulations with the general circulation model ECHAM5-HAM, including aerosol microphysics, show consequences of this warming, including changes of the quasi-biennial oscillation (QBO) in the tropics. The QBO slows down after an injection of 4 Tg(S) yr −1 and completely shuts down after an injection of 8 Tg(S) yr −1 . Transport of species in the tropics and subtropics depends on the phase of the QBO. Consequently, the heated aerosol layer not only impacts the oscillation of the QBO but also the meridional transport of the sulfate aerosols. The stronger the injection, the stronger the heating and the simulated impact on the QBO and equatorial wind systems. With increasing injection rate the velocity of the equatorial jet streams increases, and the less sulfate is transported out of the tropics. This reduces the global distribution of sulfate and decreases the radiative forcing efficiency of the aerosol layer by 10 to 14 % compared to simulations with low vertical resolution and without generated QBO. Increasing the height of the injection increases the radiative forcing only for injection rates below 10 Tg(S) yr −1 (8-18 %), a much smaller value than the 50 % calculated previously. Stronger injection rates at higher levels even result in smaller forcing than the injections at lower levels.

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Section: Model Setupmentioning

confidence: 99%

Section: Model Setupmentioning

confidence: 99%

Changing transport processes in the stratosphere by radiative heating of sulfate aerosols

2017

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“…the general circulation model (GCM) MAECHAM5 (Giorgetta et al, 2006) coupled to an aerosol microphysical module HAM-SALSA (Bergman et al, 2012;Kokkola et al, 2008), and the Max Planck Institute Earth System Model (MPI-ESM) . We investigate the simulated characteristics of the stratospheric sulfur burden, radiative forcing, and global and regional climate effects.…”

Section: A Laakso Et Al: Radiative and Climate Impacts Of A Large Vmentioning

confidence: 99%

Radiative and climate impacts of a large volcanic eruption during stratospheric sulfur geoengineering

et al. 2016

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Abstract. Both explosive volcanic eruptions, which emit sulfur dioxide into the stratosphere, and stratospheric geoengineering via sulfur injections can potentially cool the climate by increasing the amount of scattering particles in the atmosphere. Here we employ a global aerosol-climate model and an Earth system model to study the radiative and climate changes occurring after an erupting volcano during solar radiation management (SRM). According to our simulations the radiative impacts of the eruption and SRM are not additive and the radiative effects and climate changes occurring after the eruption depend strongly on whether SRM is continued or suspended after the eruption. In the former case, the peak burden of the additional stratospheric sulfate as well as changes in global mean precipitation are fairly similar regardless of whether the eruption takes place in a SRM or non-SRM world. However, the maximum increase in the global mean radiative forcing caused by the eruption is approximately 21 % lower compared to a case when the eruption occurs in an unperturbed atmosphere. In addition, the recovery of the stratospheric sulfur burden and radiative forcing is significantly faster after the eruption, because the eruption during the SRM leads to a smaller number and larger sulfate particles compared to the eruption in a non-SRM world. On the other hand, if SRM is suspended immediately after the eruption, the peak increase in global forcing caused by the eruption is about 32 % lower compared to a corresponding eruption into a clean background atmosphere. In this simulation, only about one-third of the global ensemble-mean cooling occurs after the eruption, compared to that occurring after an eruption under unperturbed atmospheric conditions. Furthermore, the global cooling signal is seen only for the 12 months after the eruption in the former scenario compared to over 40 months in the latter. In terms of global precipitation rate, we obtain a 36 % smaller decrease in the first year after the eruption and again a clearly faster recovery in the concurrent eruption and SRM scenario, which is suspended after the eruption. We also found that an explosive eruption could lead to significantly different regional climate responses depending on whether it takes place during geoengineering or into an unperturbed background atmosphere. Our results imply that observations from previous large eruptions, such as Mount Pinatubo in 1991, are not directly applicable when estimating the potential consequences of a volcanic eruption during stratospheric geoengineering.

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“…The study was performed with the general circulation model MAECHAM5 (Giorgetta et al, 2006), a middle atmosphere version of the ECHAM5 model . The model solves prognostic equations for vorticity, divergence, surface pressure and temperature, expressed in terms of spherical harmonics with a triangular truncation.…”

Section: Model Descriptionmentioning

confidence: 99%

Initial fate of fine ash and sulfur from large volcanic eruptions

et al. 2009

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Abstract. Large volcanic eruptions emit huge amounts of sulfur and fine ash into the stratosphere. These products cause an impact on radiative processes, temperature and wind patterns. In simulations with a General Circulation Model including detailed aerosol microphysics, the relation between the impact of sulfur and fine ash is determined for different eruption strengths and locations, one in the tropics and one in high Northern latitudes. Fine ash with effective radii between 1 µm and 15 µm has a lifetime of several days only. Nevertheless, the strong absorption of shortwave and long-wave radiation causes additional heating and cooling of ±20K/day and impacts the evolution of the volcanic cloud. Depending on the location of the volcanic eruption, transport direction changes due to the presence of fine ash, vortices develop and temperature anomalies at ground increase. The results show substantial impact on the local scale but only minor impact on the evolution of sulfate in the stratosphere in the month after the simulated eruptions.

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Climatology and Forcing of the Quasi-Biennial Oscillation in the MAECHAM5 Model

Cited by 239 publications

References 32 publications

Changing transport processes in the stratosphere by radiative heating of sulfate aerosols

Changing transport processes in the stratosphere by radiative heating of sulfate aerosols

Radiative and climate impacts of a large volcanic eruption during stratospheric sulfur geoengineering

Initial fate of fine ash and sulfur from large volcanic eruptions

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