Temperature and Composition Dependence of Sea Spray Aerosol Production

Abstract

Abstract A discrepancy between laboratory and field‐derived parameterizations for the dependence of sea spray aerosol (SSA) particle number concentrations ( N p ) and size distributions on water temperature ( T w ) exists. Here we address this discrepancy by quantifying the T w dependence of SSA production over the range −2–25 °C for laboratory‐generated particles using a marine aerosol reference tank (MART), a miniature MART (miniMART), and a plunging jet. Four water types were considered: NaCl water, reef salt (RS) water, filtered and autoclaved reef salt (FARS), and filtered but not autoclaved seawater (NASW). For NaCl, RS, and FARS water the N p exhibited a moderate, monotonic increase with T w for all generation methods (sensitivity of 2.1–4.1%/°C). This contrasts with some previous laboratory studies but is consistent with parameterizations derived from ambient observations. The reconciliation of laboratory results with these parameterizations supports their use in global models. The T w sensitivity also increased with particle size in the submicron size range. This indicates the fraction of primary SSA that can act as cloud condensation nuclei has a different sensitivity to T w than the total particle number. The particle production for actual seawater (NASW) differed from the other water types, exhibiting complex, irreproducible behavior with no clear T w dependence due most likely to biologically or physically driven temporal evolution of seawater composition. This suggests that variability in seawater composition may have as large an impact as temperature on actual SSA production. These observations provide new constraints and context for understanding the dependence of SSA production on water temperature and composition.