Workpackage 2

Process studies of the role of both organic and inorganic aerosol in CCN/IN

Leader: Maria Kanakidou (University of Crete, Greece)

WP2 will understand and parameterise processes associated with aerosol-cloud interactions, which are missing or are currently not well represented in ESMs. WP2 will make extensive use of results from WP1, perform process modelling at various scales to improve/develop parameterisations suitable for pristine and polluted conditions, which will be optimized for use in WP3 and WP4. Particularly WP2 aims to (i) improve the marine aerosol, including organics, and the terrestrial biogenic aerosol sources parameterisation for use in CTMs and ESMs; (ii) improve the organic aerosol representation in the models accounting for all major identified processes of OA formation and transformation in the atmosphere; (iii) develop parameterisations of primary sources of aerosols, formation and growth of CCN, ageing of aerosols by atmospheric chemical and dynamic processing. These objectives are split into four tasks:

Task 2.1: Improve existing parameterisations for the marine and terrestrial sources of aerosol.

Task 2.1 focuses on the sea-spray source function and on primary biogenic aerosol from terrestrial sources. Parameterisations related to indicators of “biological activity” (chlorophyll, terrestrial vegetation dynamic) will be developed for different environments such as the Arctic or the Amazonian rain forest. It will also assess effects of climate change and changes in atmospheric CO2 levels on fire conditions, amount of combustible litter and vegetation wildfire emissions, and provide these for ESM studies. This will be done in parallel to the development of components representing the anthropogenic aerosol contribution in polluted air masses. The work will improve existing parameterisations of these natural sources based on extensive interpretation of observations in WP1. The existing parameterisation of primary biological aerosol particles (PBAPs) will be also improved based on extensive measurements of fluorescent biological particles (FBPs) by online methods (UVAPS or WIBS) from Task 1.3. Process models will be implemented to link the observed concentrations to the emission rate.

Task 2.2: Process studies of ageing of OA and importance of natural vs. anthropogenic aerosols acting as CCN/IN.

This task focusses on understanding ageing in the atmosphere and its influence on CCN and IN properties using model simulations and statistical analyses of observations. Gas-phase, heterogeneous and aqueous/multiphase atmospheric chemistry of organics will be considered. Simplified parameterisations will be developed and tested and sensitivity modelling studies will be performed. The work involves: (i) CCN 'closure' studies of observed CCN concentrations and size distributions; (ii) analysis of the particle mixing state (internal vs. external mixtures); (iii) the effects of aerosol size, composition and semi-volatile organic compounds (SVOCs) on CCN activation and warm rain using data from WP1 and a detailed process model; (iv) exploratory descriptions of IN efficiency as a function of organic aerosol using data from laboratory experiments and the detailed process model ACPIM (Aerosol Cloud Precipitations Interactions Model) (v) the uncertainty in global CCN and cloud droplet concentrations due to uncertainties in simulated OA using a global aerosol model and new uncertainty analysis techniques.

Task 2.3 Process studies of the role of biogenic and anthropogenic organic compounds in new particle formation and growth to CCN.

The latest CERN cloud chamber data and ambient CCN/aerosol datasets will be compiled and analysed to provide appropriate parameterisations. The effects of new particle formation and growth in marine and coastal environments will be also studied using the Mace Head high-resolution aerosol mass spectrometer measurements together with aerosol microphysics and CCN measurements during open ocean particle production events. The CCN production from nucleation and organic vapour growth using the datasets constructed in Task 1.6 will be investigated. The approach of Kerminen et al. (2012) will be extended to analyse the CCN production associated with new particle formation and the role of organic vapours for particle growth from nucleation size to CCN size. The latest parameterisations of new particle formation and growth from the chamber studies will be used to evaluate the global implications using HadGEM-UKCA global model. Simulations will attempt to separate the effect of natural and anthropogenic organic precursor gases on the CCN budget.

Task 2.4: Parameterisations of CCN and IN as a function of aerosol components.

Task 2.4 will develop and test parameterisations for CCN and IN as a function of aerosol components accounting for organic aerosol impact and test them in ATHAM, CTMs and ESMs and will provide input to WP3 and WP4. This includes a physically-based parameterisation of CCN activation in the presence of semi-volatile organic carbon co-condensation to implement in a variety of models and an IN parameterisation based on field measurements, remote sensing and laboratory studies. This differs from the work in task 2.2 in that here the process model results are to be parameterised for use in large-scale models. The IN data from WP1will be the basis for the development of a parameterisation for use in ESMs. In order to take the chemical properties of the IN into account, the parameterisation will be based on laboratory studies of at least mineral dust and biological particles and validated against the field measurements of IN. Combined field measurements, remote sensing and biological/plankton laboratory studies past and future planned at Mace Head will be used to develop CCN and IN parameterisations. In WP4 these parameterisations will be included in different ESMs and validated against the in-situ and remote sensing data.

Participating institutions in WP2

Swiss Federal Institute for Technology, Switzerland University of Helsinki, Finland
University of Leeds, United Kingdom Paul Scherrer Institute, Switzerland
Max Planck Institute for Meteorology and Max Planck Institute for Chemistry, Germany National Center for Scientific Research, France
University of Manchester, United Kingdom University of Crete, Greece
National University of Ireland, Galway, Ireland National Research Council, Italy
Karlsruhe Institute for Technology, Germany