Aerosol Particle and Cloud Properties over Coastal and Marine Environments

Abstract

Climate change is arguably the largest threat currently faced by all living things on Earth, and it is widely accepted that human activities have contributed considerably to global warming trends. Rising temperatures are largely driven by deviations in atmospheric properties relative to pre-industrial conditions, including changes in greenhouse gas budgets, aerosol particle properties and burdens, and cloud radiative properties. The complex ways in which modern anthropogenic behavior has and will continue to influence the planetary energy balance are uncertain yet highly urgent to resolve as humans continue to exploit Earth’s resources unsustainably and without comprehensive knowledge of the consequences. Anthropogenically-induced changes in aerosol particles and their relationships with clouds are the largest source of this uncertainty due to the highly transient nature of these atmospheric components and the challenges involved with routinely and globally observing and/or measuring their properties and interactions. The four research papers presented in this dissertation are motivated by the demand for improved understanding of aerosol particle and cloud properties, the complex and reciprocal interactions between particles and clouds, and the individual and synergistic impacts of particles and clouds on radiative forcing, specifically over marine environments which comprise the majority of Earth’s surface area. Each paper addresses a specific void in the literature using a combination of measurements and remote sensing retrievals obtained from ground stations and during airborne research campaigns taking place at a variety of marine locations around the world. These data were used to (1) validate and identify areas for improvement in simulations of aerosol optical properties in Southeast Asia from a chemical transport model, (2) understand the influence of various air mass types on cloud condensation nuclei concentrations at a site in coastal southeast Florida, (3) investigate the seasonality of sea salt reactivity over the northwest Atlantic (NWA) and examine the significance of quantifying this reactivity using absolute values as opposed to relative values, and (4) provide the first measurements of per- and polyfluoroalkyl substances (PFAS) in cloud water collected over the NWA across a range of seasons and to identify any air mass types particularly associated with the presence of PFAS in cloud droplets. Findings from these studies are beneficial for improving understanding of aerosol particle and cloud properties in and around polluted coastal and marine environments and their effects on climate and health.