AAAR 34th Annual Conference
October 12 - October 16, 2015
Hyatt Regency
Minneapolis, Minnesota, USA
Abstract View
On the Hygroscopicity of Laboratory Generated Inorganic Sea Spray Aerosol
PAUL ZIEGER, Matthew Salter, Juan-Camillo Acosta Navarro, Joel Corbin, Martin Gysel, Evelyne Hamacher-Barth, Magnus Johnson, Caroline Leck, Douglas Nilsson, Daniel Partridge, Narges Rastak, Ilona Riipinen, Bernadette Rosati, Johan Ström, Olli Väisänen, Annele Virtanen, Josephina Werner, Stockholm University
Abstract Number: 117 Working Group: Aerosols, Clouds, and Climate
Abstract Sea spray aerosol particles were generated using both a temperature-controlled continuous plunging-jet sea spray aerosol chamber, and using nebulisers. The sea spray chamber was filled with artificial seawater free of organics whilst the nebulisers were used to generate aerosol from the same artificial seawater as well as solutions composed solely of the component salts of seawater such as NaCl and MgCl$_2. The hygroscopicity of the generated particles was determined using a Humidified Tandem Differential Mobility Analyser (HTDMA) and a humidifed nephelometer system (WetNeph). To complement these measurements, images of the particles were obtained using a scanning electron microscope (SEM), the size-segregated inorganic ion composition of the sea spray aerosol generated was determined using a 13-stage cascade low pressure impactor (LPI), and the dynamic shape factor (χ) of the generated particles was determined by measuring the mass of mobility-classified particles using a particle mass analyser.
The results are compared to theory as well as output from the E-AIM aerosol thermodynamics model using the composition of the bulk artificial seawater. Sea spray aerosol generated from the artificial seawater in the sea spray chamber exhibits 5-10% lower hygroscopic growth than both pure NaCl and the E-Aim output for particles between 50nm and 250nm. This is after correction for shape and ruling out the influence of organics.
Coincident to the laboratory experiments the sensitivity of radiative forcing to the hygroscopicity of sea spray aerosol in two large-scale earth system models has been tested. The results suggest that the lower hygroscopicity observed in our laboratory measurements has important implications for calculations of the radiative balance of the Earth given that most large-scale models currently use NaCl as a model for the hygroscopic growth of sea spray aerosol.