Periodic Reporting for period 4 - INTEGRATE (An Integrated View on Coupled Aerosol-Cloud Interactions)
Período documentado: 2024-11-01 hasta 2025-10-31
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.
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.
We explored the fundamental properties of key atmospheric trace molecules (particularly those under-explored to date, such as nitrates), and the nanoscale processes they undergo during their transport in the atmosphere. We collected and analysed data sets from different environments, putting together direct and simultaneous observational constraints on aerosol and cloud microphysics and chemistry. Based on these data, we developed numerical models of the coupled interactions between trace gases, aerosol particles and clouds, which allow for an unprecedentedly detailed - yet simple - description of the atmospheric processes coupling the hydrological cycle with the cycling of key trace species. INTEGRATE provided guidance on how these processes should be represented in climate and air quality projections, and explored the role of clouds and precipitation in determining atmospheric aerosol populations and properties. Our results highlight the importance of 1) understanding the full spectrum of aerosol number size distribution for accurate description of ACI; 2) the combination of understanding the details of aerosol population (size distribution, composition), atmospheric dynamics (particularly updrafts and moisture content) and the features of any local environment in determining interactions between clouds, aerosols and precursor gases; 3) understanding the role of hydrometeors in scavenging of gases and aerosol constituents together with simultaneous chemical processing, but also as source of new particles; 4) process-based evaluation of climate models yielding new constraints on e.g. how to represent ACI and Earth system feedbacks involving aerosol and cloud processes in simple yet accurate manner. The research conducted within INTEGRATE has been published to date in over 30 peer-reviewed scientific articles (a few manuscripts are still in press, in review or in preparation), presented in international conferences and workshops (e.g. the general assemblies of the European and American Geophysical Unions), featured in a film about an Arctic expedition, contributed to expert statements by the team members by request of media, and produced nearly 20 open data sets and model software codes.
INTEGRATE has opened new avenues for 1) fundamental understanding of the physics and chemistry of atmospheric phase transitions; 2) improved climate projections and ultimately better policies for reaching the targets of the Paris agreement; 3) better predictions of factors controlling air quality, hence facilitating the design of better policies to improve the quality of the air we breathe.
Specifically, the outcomes and new horizons opening from INTEGRATE include:
1. Improved mechanistic understanding of particle formation vs. scavenging in and near clouds. Microphysical description of cloud hydrometeor growth, coupling water condensation and ice formation with co-condensation of semi-volatile trace species, as well as condensed phase phase-separation. Simple, yet accurate approaches for treating the effects of complex aerosol particles on cloud formation in ambient conditions. Improved understanding of aerosol-cloud interactions and sensitivities in various environments.
2. Improved mechanistic understanding of aerosol and precursor gas removal and generation by clouds and precipitation. Improved estimates on the impacts of aerosol chemical composition and size distribution to the phase, radiative properties and lifetime of clouds. Budgets of aerosols and their precursors in the vicinity of clouds. Unique new data set on simultaneous observations of the composition, size distribution and dynamics of aerosol particles, cloud droplets, ice crystals and precipitation at two high-altitude locations. New modeling tools that combine state-of-the-art chemistry and dynamics.
3. Experimental and theoretical strategy for constraining atmospheric removal and deposition processes better. Improvements within atmospheric regional and global models in terms of simulating aerosol-cloud interactions, including new wet scavenging descriptions and aerosol impacts on cloud properties. Quantitative understanding of the key theoretical, observational and modeling aspects contributing to the uncertainty within the radiative forcing caused by aerosol-cloud-climate interactions.
Specifically, the outcomes and new horizons opening from INTEGRATE include:
1. Improved mechanistic understanding of particle formation vs. scavenging in and near clouds. Microphysical description of cloud hydrometeor growth, coupling water condensation and ice formation with co-condensation of semi-volatile trace species, as well as condensed phase phase-separation. Simple, yet accurate approaches for treating the effects of complex aerosol particles on cloud formation in ambient conditions. Improved understanding of aerosol-cloud interactions and sensitivities in various environments.
2. Improved mechanistic understanding of aerosol and precursor gas removal and generation by clouds and precipitation. Improved estimates on the impacts of aerosol chemical composition and size distribution to the phase, radiative properties and lifetime of clouds. Budgets of aerosols and their precursors in the vicinity of clouds. Unique new data set on simultaneous observations of the composition, size distribution and dynamics of aerosol particles, cloud droplets, ice crystals and precipitation at two high-altitude locations. New modeling tools that combine state-of-the-art chemistry and dynamics.
3. Experimental and theoretical strategy for constraining atmospheric removal and deposition processes better. Improvements within atmospheric regional and global models in terms of simulating aerosol-cloud interactions, including new wet scavenging descriptions and aerosol impacts on cloud properties. Quantitative understanding of the key theoretical, observational and modeling aspects contributing to the uncertainty within the radiative forcing caused by aerosol-cloud-climate interactions.