Linking marine phytoplankton emissions, meteorological processes and downwind particle properties with FLEXPART

Abstract

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.

North Atlantic Ocean SST-gradient-driven variations in aerosol and cloud evolution along Lagrangian cold-air outbreak trajectories

“…3.3. The black carbon concentration on both flights is consistent with previously identified clean marine conditions (< 25 ng m −3 ) (Saliba et al, 2020;Sanchez et al, 2021), and similarly the observed carbon monoxide is consistent with observations made at an eastern North Atlantic research facility that is dominated by clean marine conditions (< 130 ppb) (Zheng et al, 2018) for near-surface measurements made on both flights (Figs. S2 and S3).…”

“…It is also possible that the sulfate resided in smaller particles or more of the sulfate was removed through precipitation and subsequently more sulfate particles were formed via gas phase or in-cloud oxidation of SO 2 . Sanchez et al (2021) showed that organic aerosol mass is moderately correlated with in-water biological activity, while sulfate aerosol mass is only weakly correlated. They attributed the difference to the relatively short lifetime of the organic aerosol precursors like isoprene and monoterpenes (minutes to hours) versus sulfate precursors like DMS (> 1-2 d).…”

“…Remaining vertical levels were excluded from analysis. More details about the FLEXPART trajectories and the application to study the impact of marine biogenic particle on cloud can be found in Sanchez et al (2021).…”

“…Also, the decoupling of the boundary layer acts as a buffer, inhibiting the transfer of particles and gaseous precursors between the surface and lower free troposphere. Sanchez et al (2021) showed that organic aerosol mass is moderately correlated with in-water biological activity, while sulfate aerosol mass is only weakly correlated. They attributed the difference to the relatively short lifetime of the organic aerosol precursors like isoprene and monoterpenes (minutes to hours) versus sulfate precursors like DMS (> 1-2 d).…”

Measurement report: Cloud Processes and the Transport of Biological Emissions Regulate Southern Ocean Particle and Cloud Condensation Nuclei Concentrations

“…During this study, the CN Inv is generally greater than CN MBL , which suggests particle formation occurs more frequently above the MBL inversion, either in the FT or a decoupled layer above the marine boundary layer. Despite the lack of influence from continental and anthropogenic particles as condensational sinks in the SO, the presence of a small concentration of PMA particles can lead to a high total particle surface area (Cainey and Harvey, 2002;Sanchez et al, 2021;Yoon and Brimblecombe, 2002) and prevent NPF in the MBL. This is also shown in the histogram of the CN MBL /CN Inv ratio (Fig.…”