• ACAPS goal was to investigate and further understand the relationship of the chemical, physical, radiative and cloud nucleating properties of atmospheric aerosols. The focus was to determine the chemical, physical, and biological processes controlling the formation and fate of aerosols and how these processes affect the number size distribution, the chemical composition, and the radiative and cloud nucleating properties of aerosols.

• ACI sought to improve the understanding of the relationships between the physical and chemical properties of aerosols and the microphysical and radiative properties of the clouds that form du e to aerosol cloud condensation nuclei. Additionally, ACI studied the relationships between the physical and chemical properties of the aerosols that are processed or formed by clouds.

• ACPC was established in 2007 to obtain a quantitative understanding of the interactions between aerosol, clouds, and precipitation and their role in the climate system.

The IGAC SSC first endorsed AICI in 2003 in light of research demonstrating new processes observed in the polar regions at the air-ice interface. The goal of AICI is to assess the significance of these processes at local, regional, and global scales by bringing together the laboratory, field, and modeling communities. The first phase of AICI was very successful providing important information on the full range of processes and trace gases that are exchanged at the air/ice and snow/ice interface and how they related to atmospheric chemistry and climate.

As part of its second phase synthesis activities, the IGBP has identified several key areas which cut across research in its own core projects and which also reach out beyond IGBP with the aim of exploring future cross disciplinary research needs. The IGBP Air Pollution & Climate initiative, led by IGAC, seeks to open a science-policy dialogue on the air pollution and climate change challenge. There is still a separation between air pollution and climate change in both the policy and scientific communities.

AMMA was an international project launched in 2002 to improve knowledge and understanding of the West African Monsoon, its variability, and its impact on West African nations. Phase one of AMMA came to a completion at the beginning of 2010 and findings were published in a Special Issue of Atmospheric Chemistry and Physics. AMMA-AC during Phase 1 focused on the development of measurement networks of trace gases and aerosols throughout West Africa.

• The Aerosol Characterization Experiments, part of the larger ITCT initiative, were designed to increase our understanding of how atmospheric aerosol particles affect the Earth’s climate system. The experiments were conducted in the spring of 2001 off the coast of China, Japan and Korea. This region was of particular interest because it is downwind one of the world's largest aerosol source regions on Earth. More information regarding the findings of ACE – ASIA can be found here.

Jointly sponsored with WCRP-SPARC, AC&C sought to improve the representation of chemistry/climate interactions in models. Activities within AC&C were coordinated with modeling activities such as SPARC’s Chemistry-Climate Model Validation Activity (CCMVal), the Aerosol Comparisons between Observations and Models (AeroCom) project, and the Task Force on Hemispheric Transport of Air Pollution (HTAP) to assure maximum efficiency in model runs, meeting planning, and resources.

ACCMIP is providing extensive coordinated model simulations, diagnostics, and evaluations of the effect of short-lived species on climate, in coordination with the climate model intercomparison effort (CMIP5). The main focus is on the role of tropospheric ozone and aerosols, which both have substantial climate forcing that vary widely in space and time. More information can be found at http://www.giss.nasa.gov/projects/accmip/.

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