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Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/acp-2017-1141
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 4.0 License.
Research article
22 Dec 2017
Review status
This discussion paper is a preprint. A revision of this manuscript was accepted for the journal Atmospheric Chemistry and Physics (ACP) and is expected to appear here in due course.
Cloud, precipitation and radiation responses to large perturbations in global dimethyl sulfide
Sonya L. Fiddes1,2,3, Matthew T. Woodhouse3, Zebedee Nicholls1,4, Todd P. Lane2, and Robyn Schofield2 1Australian-German Climate and Energy College, University of Melbourne, Parkville, 3010 Australia
2ARC Centre of Excellence for Climate System Science, School of Earth Sciences, University of Melbourne, Parkville, 3010, Australia
3Climate Science Centre, Oceans and Atmosphere, Commonwealth Scientific and Industrial Research Organisation, Aspendale, 3195, Australia
4ARC Centre of Excellence for Climate Extremes, School of Earth Sciences, University of Melbourne, Parkville, 3010, Australia
Abstract. Natural aerosol emission represents one of the largest uncertainties in our understanding of the climate system. Sulfur emitted by marine organisms, as dimethyl sulfide (DMS), constitutes one fifth of the global sulfur budget and yet the distribution, fluxes and fate of DMS remain poorly constrained. In this study we quantify the role of DMS in the chemistry-climate system and determine the climate's response to large DMS perturbations. By removing all marine DMS in the Australian Community Climate and Earth System Simulator (ACCESS) – United Kingdom Chemistry and Aerosol (UKCA), we find a top of atmosphere radiative effect of 1.7 W m−2. The largest responses to removing marine DMS are in stratiform cloud decks in the Southern Hemisphere's eastern ocean basins. These regions show significant differences in low-cloud (−9 %), radiation (+7 W m−2 in short wave incoming surface radiation) and large-scale rainfall (+15 %) when all DMS is removed. We demonstrate a precipitation suppression effect of DMS-derived aerosol in stratiform cloud deck regions, coupled with an increase in low cloud fraction. The increase in low cloud fraction is an example of the aerosol lifetime effect. Other areas of low cloud formation, such as the Southern Ocean and stratiform cloud decks in the Northern Hemisphere, have a relatively weak response to DMS perturbations. Our study highlights the need for further modelling and field studies of natural aerosols and their impact on cloud and precipitation, in particular in Southern Hemisphere stratiform cloud regions.
Citation: Fiddes, S. L., Woodhouse, M. T., Nicholls, Z., Lane, T. P., and Schofield, R.: Cloud, precipitation and radiation responses to large perturbations in global dimethyl sulfide, Atmos. Chem. Phys. Discuss., https://doi.org/10.5194/acp-2017-1141, in review, 2017.
Sonya L. Fiddes et al.
Sonya L. Fiddes et al.

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Short summary
The role of natural aerosol in the climate system is uncertain. A key contributor to marine aerosol is dimethyl-sulfide (DMS), released by phytoplankton in the oceans. We study the effect of DMS on clouds and rain using a climate model with a detailed aerosol scheme. We show that DMS acts to reduce rainfall in cloud deck regions, leading to longer lived clouds and a large impact on solar energy reaching the surface. Further study of these areas will improve future climate projections.
The role of natural aerosol in the climate system is uncertain. A key contributor to marine...
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