Understanding Marine Boundary Layer Aerosol Number Budget Using Airborne Flux Measurement
AJMAL RASHEEDA SATHEESH, Nicholas Meskhidze, Markus Petters, North Carolina State University
Abstract Number: 517
Working Group: Aerosol Physics
Abstract
Quantifying the vertical distribution of aerosol over marine regions is crucial, as aerosol-cloud interaction in clean environments represents large uncertainty in radiative forcing calculations. Measurements of aerosol vertical distribution over oceans remain limited, and the relative contribution of different sources (sea spray, long-range transported anthropogenic pollution, new particle formation) to the aerosol and Cloud Condensation Nuclei (CCN) number budget in the Marine Boundary Layer (MBL) is poorly quantified.
The Azores archipelago provides a unique opportunity to study the MBL aerosol and CCN number budgets, as it represents a remote marine environment with frequent aerosol intrusions due to long-range transport. This study utilizes data collected during the Aerosol and Cloud Experiments in the Eastern North Atlantic (ACE-ENA) field campaign. The submicron particle size distribution was retrieved during June-July 2017 and January-February 2018 airborne measurements using a fast integrated mobility spectrometer and passive cavity aerosol spectrometer and merged into a single size distribution product. Particle fluxes were calculated using the Eddy Covariance technique when the airplane was in its horizontal leg and out of clouds and precipitation events.
The presentation will show fluxes of 10-30 nm and 100-1000 nm particles for several case studies. High concentrations of 10-30 nm-sized particles in FT and the negative fluxes throughout the MBL were interpreted as nucleation events with subsequent entrainment of particles into the MBL during the flights on 6 July 2017 and 7 February 2018. Frequent positive fluxes of 100-1000 nm-sized particles were indicative of sea spray emission. These fluxes, along with measurements of meteorological variables and cloud microphysical properties, are used to quantify the contribution of a) the entrainment of freshly nucleated and long-range transported particles from the FT into the MBL, and b) sea spray flux to the aerosol and CCN number budgets.