Preprints
https://doi.org/10.5194/amt-2022-46
https://doi.org/10.5194/amt-2022-46
 
11 Feb 2022
11 Feb 2022
Status: a revised version of this preprint was accepted for the journal AMT and is expected to appear here in due course.

Retrieval of the Sea Spray Aerosol Mode from Submicron Particle Size Distributions and Supermicron Scattering during LASIC

Jeramy L. Dedrick1, Georges Saliba2, Abigail S. Williams1, Lynn M. Russell1, and Dan Lubin1 Jeramy L. Dedrick et al.
  • 1Scripps Institution of Oceanography, University of California, San Diego, La Jolla, California, USA
  • 2Pacific Northwest National Laboratory, Richland, Washington, USA

Abstract. Improved quantification of sea spray aerosol concentration and size is important for determining aerosol effects on clouds and climate, though accurately capturing the size distribution of the sea spray mode remains limited by the availability of supermicron size distributions. In this paper we introduce a new approach to retrieve lognormal mode fit parameters for a sea spray aerosol mode by combing submicron size distributions with supermicron scattering measurements using a Mie inversion. Submicron size distributions were measured by an Ultra-High Sensitivity Aerosol Spectrometer (UHSAS), and supermicron scattering was taken as the difference between < 10 µm and < 1 µm 3-wavelength integrating nephelometer measurements (NEPH). This UHSAS-NEPH method was applied during background marine periods of the Department of Energy Atmospheric Radiation Measurement Layered Atlantic Smoke Interactions with Clouds (LASIC) campaign on Ascension Island (November 2016–May 2017) when the contribution of sea spray aerosol was expected to represent a large fraction of the aerosol mass and total scattering. Lognormal sea spray modal parameters were retrieved from comparisons between nephelometer measurements and a look-up table of Mie theory-simulated scattering coefficients for low error solutions that minimized the 0.4–1 µm residual in the UHSAS size distribution. The UHSAS-NEPH method retrieved sea spray mode properties for approximately 95 % of background periods during LASIC when scattering variability was low and particle concentrations were typical of the clean marine boundary layer (< 400 cm−3), ranging from 0.6 to 1.6 µm in mass mean diameter (1.3 ± 0.15 µm), 1.2 to 3.7 in modal width (2.2 ± 0.2), and mass concentration of 0.13 to 20.7 µg m−3 (6.6 ± 3.5 µg m−3). The measured nephelometer scattering at 3 wavelengths was found to only marginally constrain the mode width at the largest particle sizes in the absence of additional size and chemical measurements for defining parameters for the Mie solutions. Comparing UHSAS-NEPH retrievals to those of a fitting algorithm applied only to the submicron UHSAS number size distribution showed that correlations between retrieved mass concentration and the available mass-based sea spray tracers (coarse scattering, wind speed, and chloride) are low when supermicron measurements are not considered. We also show that measured supermicron size distributions are needed to adequately characterize the sea spray number concentration, though mass concentration can be comparably characterized using the supermicron scattering. This work demonstrates the added value of supermicron scattering measurements for retrieving reasonable sea spray mass concentrations, providing the best-available, observationally-constrained estimate of the sea spray mode properties when supermicron size distribution measurements are not available.

Jeramy L. Dedrick et al.

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on amt-2022-46', Anonymous Referee #1, 16 Mar 2022
  • RC2: 'Comment on amt-2022-46', Anonymous Referee #2, 20 Mar 2022

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on amt-2022-46', Anonymous Referee #1, 16 Mar 2022
  • RC2: 'Comment on amt-2022-46', Anonymous Referee #2, 20 Mar 2022

Jeramy L. Dedrick et al.

Data sets

Retrieved Sea Spray Aerosol Fitting Parameters from LASIC and NAAMES Jeramy L. Dedrick, Georges Saliba, Abigail S. Williams, Lynn M. Russell, Dan Lubin https://github.com/jdedrick95/get_sea_spray_mode

Model code and software

Sea Spray Mode Retrieval and Mie Scattering Codes Jeramy L. Dedrick, Georges Saliba, Abigail S. Williams, Lynn M. Russell, Dan Lubin https://github.com/jdedrick95/get_sea_spray_mode

Jeramy L. Dedrick et al.

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Short summary
A new method is presented to retrieve the sea spray aerosol size distribution by combing submicron size and nephelometer scattering based on Mie theory. Using available sea spray tracers, we find that this approach serves as a comparable substitute to supermicron size distribution measurements, which are limited in availability at marine sites. Application of this technique can expand sea spray observations and improve the characterization of marine aerosol impacts on clouds and climate.