Linking marine phytoplankton emissions, meteorological processes and downwind particle properties with FLEXPART
Authors: Sanchez Kevin J. , Zhang Bo , Liu Hongyu , Saliba Georges , Chen Chia-Li , Lewis Savannah L. , Russell Lynn M. , Shook Michael A. , Crosbie Ewan C. , Ziemba Luke D. , Brown Matthew D. , Shingler Taylor J. , Robinson Claire E. , Wiggins Elizabeth B. , Thornhill Kenneth L. , Winstead Edward L. , Jordan Carolyn , Quinn Patricia K. , Bates Timothy S. , Porter Jack , Bell Thomas G. , Saltzman Eric S. , Behrenfeld Michael J. , Moore Richard H. 
Published: September 2020

Abstract. Marine biogenic particle contributions to atmospheric aerosol concentrations are not well understood though they are important for determining cloud optical and cloud nucleating properties. Here we examine the relationship between marine aerosol measurements with satellite and model fields of ocean biology and meteorological variables during the North Atlantic Aerosols and Marine Ecosystems Study (NAAMES). NAAMES consisted of four field campaigns between November 2015 and April 2018 that aligned with the four major phases of the annual phytoplankton bloom cycle. The FLEXPART Lagrangian particle dispersion model is used to connect these variables spatiotemporally to ship-based aerosol and dimethyl sulphide (DMS) observations. We find that correlations between some aerosol measurements with satellite measured and modelled variables increase with increasing trajectory length, indicating biological and meteorological processes over the air mass history are influential to measured particle properties and that using only spatially contemporaneous data would miss correlative connections that are lagged in time. In particular, the marine non-refractory organic aerosol mass correlates with modelled marine net primary production when weighted by 5-day air mass trajectory residence time (r = 0.62). This result indicates non-refractory organic aerosol mass is influenced by biogenic volatile organic compound (VOC) emissions from photosynthesis by phytoplankton stocks during advection into the region. This is further supported by the correlation of non-refractory organic mass with 2-day residence-time-weighted chlorophyll-a (r = 0.39), a proxy for phytoplankton abundance, and 5-day residence-time-weighted downward shortwave forcing (r = 0.58), a requirement for photosynthesis. In contrast, DMS (formed through biological processes in the seawater) and primary marine aerosol (PMA) concentrations showed better correlations to explanatory biological and meteorological variables weighted with shorter air mass residence times, which reflects their localized origin as primary emissions. Aerosol submicron number and mass negatively correlate with sea surface wind speed. The negative correlation is attributed to enhanced PMA concentrations under higher wind speed conditions. We hypothesized that the elevated total particle surface area associated with high PMA concentrations leads to enhanced rates of VOC condensation onto PMA. Given the high deposition velocity of PMA, relative to submicron aerosol, PMA can limit the accumulation of secondary aerosol mass. This study provides observational evidence for connections between marine aerosols and underlying ocean biology through complex secondary formation processes, emphasizing the need to consider airmass history in future analyses.