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Ciarlo`, J. (ongoing)
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Ciarlo`, J. (ongoing). Ph.D. Project. Modelling the Formation and Radiative Effects of Secondary Organic Aerosols in a Climate Model.

Supervisor: Dr N. Aquilina

Project Description

The presence of organic aerosols in areas affected by anthropogenic pollution, on many occasions, is second only to sulfate aerosols, and observations suggest that organic aerosols are the most important contributors to light scattering. They can be directly emitted into the atmosphere or produced by oxidation of a gaseous precursor; the latter are called secondary organic aerosols (SOA). Several phenolic compounds in the aqueous phase were found to produce large quantities of highly oxygenated SOA; these are likely to have an important role in the aerosol-cloud interactions.

Most climate models, in their calculations of projections of future atmospheric conditions take into account non-volatile particulate primary organic aerosols (POA). SOA are now starting to be included in several models, and were found to minimize biases for organic aerosol mass and aerosol optical depth. When compared to available observations, the bias of climate models, for parameters directly or indirectly influenced by aerosols are still high and considerable amount of research is required to further improve the performance of climate models. The RegCM4 model considers chemistry calculations involving aerosols, sulfates, organic and black carbons, however research into the implementation of more detailed chemistry calculations is still in development.

This project proposal suggests developments to be included in the current version of the RegCM4 model. These include introducing SOA precursors depending on laboratory data and emission inventories; including SOA formation in the particle and aqueous phase; including acid-catalysed reactions; introducing aerosol/cloud interactions; and also possibly the ageing of SOA. The main focus will be given to the following VOCs: acetylene, toluene, xylene, benzene, isoprene, and terpenes. This study shall be conducted in order to implement known chemical reactions of organic aerosols in the RegCM4 model. The physical conditions that control the yield of formation of SOA should also be implemented in the model.

It is widely understood that aerosols have a negative radiative forcing on the incoming radiation due to their scattering properties of shortwave radiation. However, carbonaceous aerosols have a positive radiative forcing due to their absorbing properties. The organic nature of the SOA, as well as their variation in size and structure, significantly alters the physical properties of these particulates such as the enthalpy of vaporization.

Climate simulations will be conducted on a few geographic regions, with and without the new chemistry scheme in order to test out its validity. Incorporating these SOA processes in the existing chemical scheme of the RegCM4 model will possibly help reduce the biases of the model and also possibly provide further insight in the effects of organic species in the atmosphere, currently not taken into consideration by the model.

Department Transfer
As of 1 October 2015, the CRG has been transferred to the new Department of Geosciences.
Air Quality Mobile Laboratory
The acquisition of an air quality monitoring van has started a new research branch within the group.
International Contribution
A CRG researcher is contributing to development of a new gas-phase-to-aerosol scheme in the state-of-the-art Regional Climate Model, RegCM4.
Last Updated: 7 October 2015

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