New Methodology for Deriving Super-micron Sea Salt Aerosol Number and Flux Values Using Doppler Lidar Measurements
Tyas Pujiastuti, NICHOLAS MESKHIDZE, Markus Petters, North Carolina State University
Abstract Number: 376
Working Group: Remote and Regional Atmospheric Aerosol
Abstract
Previous studies have shown that super-micron sea salt aerosols (SSA) can impact cloud microphysical properties and induce drizzle and warm rain formation in stratocumulus clouds. Despite their importance, our knowledge of super-micron SSA particle fluxes, vertical distribution, production mechanisms, and spatiotemporal distribution in the marine boundary layer remains limited. Here we report measurements of remotely sensed size-selected (with ambient diameter between 1 and 10 μm) particle number concentration and production flux. The data were collected during the Eastern Pacific Cloud Aerosol Precipitation Experiment (EPCAPE) campaign at Scripps Pier, La Jolla, California, from 15 April to 30 September 2023. The aerosol size distribution was acquired from surface measurements by an optical particle counter, and vertical profiles of vertical velocity and attenuated backscatter were obtained from a Doppler lidar. The data were reduced for cloud-free conditions with onshore winds ≥ 4 m s-1.
By combining super-micron aerosol number size distributions measured at the pier with the Mie theory-calculated relationship between particle number concentration and backscatter, we derived the super-micron (plausibly SSA) number concentration and size distribution at 105 m height (minimum usable range for the Doppler lidar) above the ocean surface. The derived number concentration ranged from 0.3 to 1.6 cm-3, and the production flux (calculated using the Eddy Covariance method) ranged from 0.1 cm-2 s-1 to 1.25 cm-2 s-1 for different surface wind speeds. The size-selected fluxes exhibited a pattern similar to the size distribution. The highest flux was derived for 1.02 μm particles and declined exponentially for the larger sizes. The particle number concentrations and derived fluxes are comparable with the available SSA parameterizations. This presentation will discuss how this novel methodology based on remotely-sensed data for deriving size-selected super-micron aerosol number concentration and production flux values can be applied over different ocean regions.