Atmos. Chem. Phys. Discuss., 9, 5447-5464, 2009
www.atmos-chem-phys-discuss.net/9/5447/2009/
doi:10.5194/acpd-9-5447-2009
© Author(s) 2009. This work is distributed
under the Creative Commons Attribution 3.0 License.
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This discussion paper has been under review for the journal Atmospheric Chemistry and Physics (ACP). Please refer to the corresponding final paper in ACP.
The climatic effects of the direct injection of water vapour into the stratosphere by large volcanic eruptions
M. M. Joshi1 and G. S. Jones2
1Walker Institute for Climate System Research, University of Reading, UK
2Hadley Centre for Climate Change, Met Office, UK

Abstract. We describe a novel mechanism that can significantly lower the amplitude of the climatic response to certain large volcanic eruptions. The proximity of oceans to some volcanoes can cause significant entrainment of water into coignimbrite clouds during the eruption. If sufficiently large amounts of this entrained water vapour enter the stratosphere, a climatically significant amount of water vapour can be left over in the lower stratosphere after the eruption, even after sulphate aerosol formation. This excess stratospheric humidity warms the climate, and acts to balance the climatic cooling induced by the volcanic aerosol, especially because the humidity anomaly lasts for a period that is longer that the residence time of aerosol in the stratosphere. In particular, Northern Hemisphere cooling is reduced in magnitude. We discuss this mechanism in the context of the discrepancy between the observed and modelled cooling following the Krakatau eruption in 1883.

Citation: Joshi, M. M. and Jones, G. S.: The climatic effects of the direct injection of water vapour into the stratosphere by large volcanic eruptions, Atmos. Chem. Phys. Discuss., 9, 5447-5464, doi:10.5194/acpd-9-5447-2009, 2009.
 
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