+ Narrowing the uncertainty in climate prediction by quantifying the roles of aerosols, clouds, and aerosol-cloud-precipitation interactions in coupling the Earth's hydrologic and energy cycles, and in climate change.
+ Measuring the ocean ecosystem changes and precisely quantifying ocean carbon uptake.
+ Improving air quality forecasting by discriminating aerosol types, as well as their distributions with height, for input into transport and process models.
The Earth System has many intertwined feedback loops and many of these introduce nonlinear interactions. Below we present a simplified view into a much more complex system, but nonetheless retain a few key processes related to ACE.
Since CO2 is a greenhouse gas, its concentration influences the atmosphere equilibrium temperature. When CO2 concentration increases in the atmosphere its temperature is likely to rise. Risen temperature in turn increases the atmosphere's capacity to hold moisture, i.e. water vapor, which is itself a greenhouse gas. With other things being equal, this leads to a positive feedback and even warmer temperature.
However, higher humidity may also result in more clouds, which are composed of water condensates. Since clouds reflect solar radiation they reduce solar energy reaching to the lower part of Earth's atmosphere and surface, and thereby exert a cooling effect. At the same time, they blanket the Earth and lead to compensating warming through their greenhouse effect in the infrared. Locally, the net effect can be warming or cooling, and can be different for the surface and atmosphere.
Aerosols, minute particles suspended in air, similarly reflect and absorb solar energy. The former tends to cool the surface while the latter warms the atmosphere. Moreover, the formation of clouds depends not only on the availability of water vapor but also the presence of cloud condensation and/or ice nuclei (CCN or IN) and dynamical forcing. Atmospheric warming due to solar absorption by aerosols can significantly affect the dynamical forcing. With aerosols acting as CCN, more CCN lead to smaller drops and higher cloud reflectivity, which further reduce solar energy intake. Since for a cloud to precipitate, the cloud drops must grow dramatically, smaller cloud particles may delay the process through increased competition for the available vapor. Smaller and more numerous cloud droplets may also affect the transition from liquid to ice phase that is so crucial to the formation of precipitation. Aerosols acting as IN also have a strong effect on details of the liquid-to-ice transition and precipitation processes.
Ocean ecosystems are important processors of CO2 through photosynthesis. They also play a key role in storing the carbon element as their denizens die and sink, taking their carbon as sediment to ocean floor. Therefore the productivity of the ocean ecosystems can directly impact atmospheric CO2 concentration.
The productivity of the ecosystems increases as nutrients for their growth increase. Dust aerosols with rich iron content are such nutrients. Land surfaces and human activities are major source of these aerosols. Drought conditions, due to the lack of precipitation and often associated with higher temperature, increase the abundance of these aerosols, which may be transported, by wind directly or indirectly via precipitation from cloud systems with condensates containing dust aerosols as CCN, to the parts of the ocean with active ecosystems. This wind transport of ocean ecosystem "fertilizer" is called "aeolian fertilization."
Additionally, biochemical processes of the ocean ecosystems, as well as physical processes of the ocean (such as waves and foams), produces aerosols that can act as CCN or IN, which, as mentioned above, interact in turn with cloud formation.