Meteorological Control of Aerosol–Cloud–Radiation Interactions Across Cloud Regimes and Scales

Abstract

Marine low clouds exert a dominant influence on Earth’s planetary albedo and remain a primary source of uncertainty in estimates of aerosol forcing and cloud–climate feedback. Small changes in cloud radiative cooling, precipitation, or boundary-layer structure can substantially alter regional and global energy balance. Yet the sensitivity of these clouds to aerosol perturbations is not fixed, and varies widely across dynamical regimes and stages of cloud evolution. Understanding how aerosol effects emerge from the interaction between microphysical perturbations and background meteorology is therefore central to reducing uncertainty in cloud–radiation coupling. This dissertation investigates aerosol sensitivity across idealized and evolving marine boundary layer regimes by integrating process-resolving simulations with observation-based analyses. Using large-eddy simulations of idealized, near-overcast stratocumulus clouds, the first part of this work quantifies how turbulence, precipitation, and cloud radiative effect respond to aerosol loading under varying large-scale meteorological conditions. The results demonstrate that aerosol-induced modifications of radiative cooling and boundary-layer evolution depend strongly on the background boundary layer meteorological and aerosol conditions. The analysis is then extended to the stratocumulus-to-cumulus transition, a regime in which cloud organization and boundary-layer coupling evolve rapidly. Simulations in this part of the analysis show that limited-domain configurations, when decoupled from interactive large-scale adjustment, can systematically overestimate cloud radiative cooling responses to aerosol perturbations. These findings highlight the critical role of large-scale dynamical coupling in constraining aerosol-induced cloud evolution during regime transitions. To bridge process-level understanding with real-world variability, the final part of this dissertation employs satellite observations within a Lagrangian, trajectory-based framework to quantify cloud sensitivity to aerosol across regional and seasonal meteorological states. By tracking cloud evolution along air-mass trajectories and decomposing cloud radiative effects into first- and second-order contributions, this analysis reveals systematic, state-dependent variability in aerosol–cloud radiative responses that is consistent with, but extends beyond, insights derived from idealized simulations. Collectively, this body of work demonstrates that aerosol sensitivity is an emergent, state-dependent property of marine low clouds, shaped by the interplay between microphysics, turbulence, precipitation, and large-scale dynamical context. By combining process-based large-eddy simulations with satellite-constrained, trajectory-based diagnostics, the dissertation provides a unified and physically grounded framework for understanding how aerosol perturbations translate into radiative responses in the climate system.