Abstract
Sea spray is one of the largest natural aerosol sources and plays an important role in the Earth’s radiative budget. These particles are inherently hygroscopic, that is, they take-up moisture from the air, which affects the extent to which they interact with solar radiation. We demonstrate that the hygroscopic growth of inorganic sea salt is 8–15% lower than pure sodium chloride, most likely due to the presence of hydrates. We observe an increase in hygroscopic growth with decreasing particle size (for particle diameters <150 nm) that is independent of the particle generation method. We vary the hygroscopic growth of the inorganic sea salt within a general circulation model and show that a reduced hygroscopicity leads to a reduction in aerosol-radiation interactions, manifested by a latitudinal-dependent reduction of the aerosol optical depth by up to 15%, while cloud-related parameters are unaffected. We propose that a value of κs=1.1 (at RH=90%) is used to represent the hygroscopicity of inorganic sea salt particles in numerical models.
Highlights
Sea spray is one of the largest natural aerosol sources and plays an important role in the Earth’s radiative budget
The sea salt particles generated by the nebulizer are closer to perfect cubes than the sea salt particles generated by the sea spray chamber, indicating that the generation method influences particle shape
The supermicrometre ks values are consistent with the submicrometre values, which adds support to the view that the hygroscopicity of inorganic sea salt particles is not equal to that of NaCl and instead is measurably reduced. For simplified applications, such as model parameterizations, we suggest that a value of ks 1⁄4 1.1 at relative humidity (RH) 1⁄4 90% is used to represent inorganic sea salt aerosol particles
Summary
Sea spray is one of the largest natural aerosol sources and plays an important role in the Earth’s radiative budget. The ability of particles to take up water, termed hygroscopicity, is determined by the particle’s size and chemical composition It is an important quantity as it influences the magnitude of the direct aerosol radiative forcing[6] since ambient aerosol optical properties will depend on the ambient relative humidity (RH)[7]. The reduction in hygroscopic growth relative to NaCl that is often observed in ambient measurements in the remote marine atmosphere is generally attributed solely to the contribution of internally mixed organic substances[11]. This assumption is not easy to validate for a number of reasons. Laboratory measurements of the hygroscopicity of sea salt often suffer from significant diversity in the measured values, lack of detail in measurement descriptions, and differences in particle production techniques (see Supplementary Table 1 for an overview)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
