Impact of the QBO phases on transport of sulfate aerosols in the stratosphere

Thursday, 22 March 2018
Iriarte (Hotel Botanico)
Ulrike Niemeier1, Claudia Timmreck1, Kirstin Krüger2 and Hauke Schmidt1, (1)Max Planck Institute for Meteorology, Hamburg, Germany, (2)University of Oslo, Oslo, Norway
Abstract:
The lifetime of stratospheric sulfate aerosols and their transport depends on aerosol microphysical processes, the related particle size, sedimentation and transport. These parameters differ clearly between models causing, e.g. a wide range of radiative forcing of stratospheric aerosols after stratospheric sulfur injections (Niemeier and Tilmes, 2017). Marshall et al (2017) show up to 10 months difference between the time of occurrence of the global maximum sulfate burden after a simulated Tambora-like eruption in an intercomparison of four aerosol climate models. Beside aerosol microphysics, stratospheric dynamics, e.g the representation of the quasi biennial circulation (QBO), are not the same in these models. One of them, ECHAM5-HAM, does not generate a QBO in the applied version. Increasing the vertical resolution (L90), which generates a QBO, allows to determine the impact of the vertical model resolution on the lifetime of sulfate in ECHAM5.

Transport processes in the stratosphere depend on the QBO phase. A westerly phase in the lower stratosphere increases tropical confinement of the aerosols and reduced meridional transport (Niemeier and Schmidt, 2017). We investigate the impact of the QBO phase on the distribution of sulfate after a volcanic eruption in different case studies in simulations with eruptions in different QBO phases. Simulations of a hypothetical Mt. Agung eruption in October 2017, once into a freely developed QBO in a phase similar to observations and once into a zonal wind field nudged to observations, show different meridional transport. We further analyse if the relatively short life time of the sulfate in ECHAM5-HAM after the simulated Tambora eruption (Marshall et al, 2017) increases in the configuration that generates.

Marshall, L., et al.: ACPD, https://doi.org/10.5194/acp-2017-729, 2017.

Niemeier, U. and Schmidt, H.:, ACPD, doi.org/10.5194/acp-2017-470, 2017.

Niemeier U. and S. Tilmes, Science, Vol. 357, Issue 6348, pp. pp 246-248, DOI: 10.1126/science.aan3317, 2017.

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