The ACE-1 scientific objectives will be addressed in several activities during the intensive measurement campaign and during the transit flights and cruise between the United States and Australia. Six research questions, outlined in section 2.1, have been defined to address these objectives. The strategies for answering these 6 questions are outlined in this chapter. Chapter 5 contains the specific approaches that will be used to implement these strategies, with the necessary instruments and platforms described in Chapter 4.

The ACE-1 scientific objectives and related research questions are directed toward the overall ACE goal: to provide the necessary data to incorporate aerosols into global climate models and to reduce the uncertainty in the calculation of climate forcing by aerosols. A critical part of aerosol radiative forcing calculations involves relating the size-dependent chemical composition of aerosols to their radiative impact. In models, this module makes the critical link between anthropogenic changes in the chemical composition of the atmosphere and the associated impact on the Earth's radiation budget. Questions 1 and 2 address Objective 1 and are meant to provide data to test and validate aerosol/climate models on local and column-integrated scales.

Process studies are also needed to evaluate the factors controlling the sources, formation and fate of aerosols and the way these processes affect the number size distribution, chemical composition, and radiative and cloud nucleating properties of the particles. Questions 3, 4 and 5 address Objective 2 and relate to models of the natural biogeochemical processes that create atmospheric sulfate and its precursors and the processes that control the aerosol population. Finally, question 6, which addresses Objective 3, integrates the closure experiments and process studies into models on a variety of scales.