Overview of the Antarctic Circumnavigation Expedition: Study of Preindustrial-like Aerosols and Their Climate Effects (ACE-SPACE)
Abstract
Aerosol-cloud interactions are the least understood anthropogenic influence on climate change. A major cause of this limited understanding is the poorly quantified state of aerosols in the pristine preindustrial atmosphere, which defines the baseline against which anthropogenic effects are calculated.
This contribution gives an overview of the ACE-SPACE project, which was part of the Antarctic Circumnavigation Expedition and whose main purpose was to conduct a comprehensive aerosol characterization in preindustrial-like conditions over the Southern Ocean between December 2016 and March 2017, recording aerosol data in some regions for the first time. The data set is not only of interest to understand atmospheric processes under pristine conditions, but also to validate satellite retrievals of aerosol properties and model simulations, which are both essentially unconstrained over the Southern Ocean. We will present aerosol microphysical and chemical properties, discuss particle origin - including new particle formation - and compare the in-situ measurements with satellite retrievals and model simulations. Important factors influencing aerosol properties were meteorology and ocean biological activity: For instance, the leg between South Africa and Australia experienced a series of low-pressure systems characterized by a significant fraction of Nucleation and Aitken mode particles. Contrary to previous observations, the small mode dominated the size distribution under calmer conditions and was not necessarily associated with air mass trajectories arriving from higher altitudes. Near the West-Antarctic coast between Australia and South America, accumulation mode particles dominated the size distributions that were associated with open ocean air masses and likely cloud processing due to the pronounced Hoppel Minimum. The mode contained methanesulfonic acid, a product from phytoplankton related dimethylsulfid emissions and showed the highest CCN activation ratio at 0.2 % supersaturation. Both the global aerosol model as well as the satellite observations underestimate the number concentration of CCN in specific sectors of the Southern Ocean where the main particle source seems to come from the surface but is not necessarily sea spray.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.A11B..01S
- Keywords:
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- 0305 Aerosols and particles;
- ATMOSPHERIC COMPOSITION AND STRUCTUREDE: 0320 Cloud physics and chemistry;
- ATMOSPHERIC COMPOSITION AND STRUCTUREDE: 3310 Clouds and cloud feedbacks;
- ATMOSPHERIC PROCESSESDE: 3349 Polar meteorology;
- ATMOSPHERIC PROCESSES