INTEGRATE dealt with understanding and describing the interactions between atmospheric aerosol particles, clouds and precipitation. Besides being central for understanding of the fundaments of the Earth’s atmosphere, they represent a key uncertainty in climate projections and have implications for air quality and health – clouds and precipitation being the most important sinks removing hazardous particulate matter from the atmosphere. Cloud formation processes, specifically 1) the interplay between the phase transitions upon cloud formation; 2) the interactions between atmospheric chemical composition and dynamics; are poorly understood. This hampers the efforts to constrain the impacts clouds have on aerosol populations (albeit known to be both sources and sinks of particles) and the effects changing aerosol populations have on cloud properties. Poor constraints on these coupled aerosol-cloud interactions (ACI) lead to lacking knowledge on the role that clouds play in the climate system, their role in governing air quality in different environments, and the interactions between future air quality and climate change mitigation measures. INTEGRATE was based on the assumption that a major reason for these uncertainties are inconsistencies and discontinuities in treating 1) the molecular phase transitions from the gas phase to the largest hydrometeors; 2) the interplay between atmospheric chemical composition and atmospheric dynamics; 3) the complex role that clouds play as the main sink of particulate matter, sources of new particles, but also as subjects to changes driven by aerosol particles. INTEGRATE connected the key pieces together through work in 1) the process scale, focusing on the phase transitions happening within clouds; 2) the cloud scale, focusing on the integration of relevant chemical and dynamic phenomena; 3) the regional and global scales, focusing on interactions between aerosol loadings and clouds in past, present and future climates. INTEGRATE relied of the thesis that fundamental theory should be developed hand-in-hand with the tools used to project air quality changes and climate. Systematic approaches for bridging the gap between the various time and spatial scales involved are the key to achieve this.
The overall objectives of INTEGRATE were (see Fig. 1):
O1. Bridging key knowledge gaps in the thermodynamics and kinetics of the interactions between aerosol particles, cloud hydrometeors (water and ice) and the gas phase.
O2. Developing computational techniques for describing aerosols and clouds, accounting for detailed chemistry and microphysics coupled to atmospheric dynamics.
O3. Investigating the net interactions between clouds and aerosol populations in the past, present and future climates.
O4. Systematic simplification and scaling of key processes – which are often too complex to represent from first principles in models used for climate projections or air quality studies.
During the course of the project, INTEGRATE contributed to all these objectives, demonstrating a new way to view ACI: as a continuum from the molecular to the macroscopic scales.
