Estimation of Sea Spray Aerosol Surface Area Over the Southern Ocean Using Scattering Measurements
Abstract
This study focuses on methods to estimate dry marine aerosol surface area (SA) from bulk optical measurements. Aerosol SA is used in many models' ice nucleating particle (INP) parameterizations, as well as influencing particle light scattering, hygroscopic growth, and reactivity, but direct observations are scarce in the Southern Ocean (SO). Two campaigns jointly conducted in austral summer 2018 provided co‐located measurements of aerosol SA from particle size distributions and lidar to evaluate SA estimation methods in this region. Mie theory calculations based on measured size distributions were used to test a proposed approximation for dry aerosol SA, which relies on estimating effective scattering efficiency (Q) as a function of Ångström exponent (å). For distributions with dry å Q = 2 was found to be a good approximation within ±50%, but for distributions with dry å > 1, an assumption of Q = 3 as in some prior studies underestimates dry aerosol SA by a factor of 2 or more. We propose a new relationship between dry å and Q, which can be used for −0.2 å å = 0.8 as the cutoff between primary and secondary marine aerosol‐dominated distributions. Application of a published methodology to retrieve dry marine aerosol SA from lidar extinction profiles overestimated aerosol SA by a factor of 3–5 during these campaigns. Using Microtops aerosol optical thickness measurements, we derive alternative lidar conversion parameters from our observations, applicable to marine aerosol over the SO.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- Nov 20, 2022
- Source ID
- 10.1029/2022jd037009
Entities
People
- Alain Protat
- J. B. Jensen
- J. Michael Reeves
- Kathryn A Moore
- Kevin J Sanchez
- Paul DeMott
- Ruhi Humphries
- Simon Alexander
- Sonia Kreidenweis
Organizations
- Australian Antarctic Division
- Bureau of Meteorology
- Colorado State University
- Commonwealth Scientific and Industrial Research Organisation
- Langley Research Center
- National Center for Atmospheric Research
- National Science Foundation
- United States Department of Energy
- University of Tasmania