UC San Diego

Sea spray aerosols (SSA) are the most-abundantly emitted natural aerosol on the planet and drive climate through direct and indirect interactions with radiation. SSA modify cloud microphysical properties (including albedo, lifetime, and precipitation propensity) leading to complex and non-linear interactions with radiation, causing aerosol-cloud interactions to remain one of the least constrained elements of the global radiative energy budget. This dissertation targets three primary uncertainties of SSA production processes which complicate estimating aerosol-cloud interactions: ranges of simulated SSA emissions in Earth System models (ESMs), laboratory replication techniques of breaking waves for SSA production, and quantification of the roles of environmental variables driving SSA emissions. To estimate aerosol-cloud interaction radiative forcing, SSA are simulated in ESMs through integration of SSA emission parameterizations. The first chapter of this dissertation documents the range of simulated SSA variance in 17 ESMs, emphasizing factors contributing to disagreements of up to eight orders of magnitude for coarse mode particle number flux emissions, and concludes with targeted recommendations for a diverse range of approaches seeking to better understand SSA emissions. One approach is improved replication of the ocean-atmosphere interface (OAI) in the laboratory, generating SSA emissions under controlled environments. The second chapter of this work details the Scripps Ocean-Atmosphere Research Simulator (SOARS), a new simulator offering a cohesive suite of environmental controls enabling replication of surface ocean conditions spanning the globe. Chapter three utilizes SOARS to measure SSA in the laboratory, characterizing SOARS for all future aerosol measurements. Measurements of SSA emission flux in SOARS are used in chapter four to adjust parameterizations used in the Energy Exascale Earth System Model (E3SM), correcting a default emission scheme that underestimates SSA emissions. Finally, chapter five explores the role of sea surface temperature on SSA emissions, where increasing temperatures from 2 to 23 oC suppresses SSA emissions by a factor of four. A feedback parameter is generated which can be implemented in ESMs to further correct the biased SSA emissions. This work characterizes the current understanding of SSA emissions and offer guidance to further improve laboratory generation and model simulation of SSA.