AbstractAerosol-cloud interactions constitute the largest uncertainty in current and future climate predictions. Thus, it is essential to obtain a more detailed fundamental understanding of these processes. It is well-established that sea spray aerosols (SSA) are one of the largest natural sources of aerosol mass in the atmosphere. Currently the literature is lacking in its understanding of SSA formation processes and properties important for cloud formation.
Using sea spray simulation chambers, we investigated the effect of air entrainment, temperature and algal biomass on SSA formation and study bioaerosolisation from a bubble bursting environment. In addition, SSA properties, such as size distributions, hygroscopic growth, cloud droplet formation and ice nucleation activity, are probed using state-of-the-art measurement techniques.
Our main findings show that air entrainment rate is correlated with SSA production, and that the relationship between seawater temperature and aerosol production differs depending on whether a plunging jet or diffuser is used to simulate the SSA generation process. Investigating the aerosolisation of bioaerosols, we observed a 10-fold higher fraction of surviving cells when dried as aerosol compared to when dried on a surface. We performed targeted laboratory experiments elucidating the hygroscopicity of freshly produced SSA, and found that the inorganic sea salt fraction dominates the cloud-forming ability. However, we also show that aged SSA might be substantially less hygroscopic with respect to particles with smaller diameters (50 nm).
We highlight that the heterogeneous ice nuclei activity of SSA generated from Arctic sea surface microlayers and two algal cultures, Skeletonema marinoi and Melosira arctica, is relatively poor compared to other relevant ice nucleating particle sources. Finally, we show that simulated Arctic mixed-phase cloud properties are relatively insensitive to the hygroscopicity parameter, κ, above 0.4, indicating that internal mixing of biogenic organics in SSA has a relatively small influence on cloud droplet activation.
|Date of Award||23 Oct 2020|
|Supervisor||Merete Bilde (Supervisor)|
- Sea Spray Aerosol