An Overview of Atmospheric Features Over the Western North Atlantic Ocean and North American East Coast – Part 1: Analysis of Aerosols, Gases, and Wet Deposition Chemistry

Abstract

The Western North Atlantic Ocean (WNAO) and the adjoining East Coast of North America have been the focus of numerous efforts aimed at understanding their atmospheric processes, with a particular emphasis on atmospheric chemistry and aerosol characterization. Over 50 field campaigns and long-term monitoring programs have been conducted in this broad region and summarized in over 700 peer-reviewed publications (Sorooshian et al., 2020). That review article highlighted important regional atmospheric features and identified knowledge gaps that warrant further research. North American pollution and outflow over the WNAO have been of interest for reasons such as acid rain (e.g., Cogbill & Likens, 1974; Likens & Bormann, 1974) and the opportunity to examine the aging of gas and aerosol pollutants (e.g., Fehsenfeld et al., 2006). Bermuda in particular has been a scientifically critical island where an extensive amount of research has been conducted over the last several decades to monitor changes in variables associated with pollution, climate, and general atmospheric changes (Aryal et al., 2014; Keene et al., 2014). The Sargasso Sea around Bermuda has also been the subject of many efforts intended to examine air-sea interaction processes, aerosol deposition,

An Aerosol Climatology and Implications for Clouds at a Remote Marine Site: Case Study Over Bermuda

“…One way to reconcile the lack of fine particulate pollution and enhanced density of trajectories coming from North America in DJF is that the highest cloud fractions and precipitation occur in DJF over the WNAO (Painemal et al, 2021), and thus there may be extensive wet removal of transported aerosols from North America. MERRA-2 data over the WNAO region (2014WNAO region ( -2018 shows that the highest sea salt AOTs occur in DJF and SON, with the lowest values in JJA (Corral et al, 2021), consistent with our FMF results.…”

Cloud drop number concentrations over the western North Atlantic Ocean: seasonal cycle, aerosol interrelationships, and other influential factors

“…The seasons with the greatest AOD values, accompanied by the most pronounced spatial gradient offshore, were JJA and MAM. The offshore gradient owes to continental pollution outflow ( Corral et al, 2021 , and references therein). In contrast, DJF and SON exhibited lower AOD values with a distinct area of higher AOD values offshore between ~ 35–40° N accounted for by sea salt.…”

“…Bermuda stands out as having the highest AOD fractional contributions in the PBL in DJF (72 %) and SON (69 %) and among the highest seasonal total AODs in those two seasons (0.14 in DJF and 0.10 in SON) assisted in large part by sea salt ( Fig. 3 ) ( Aldhaif et al, 2021 ), coincident with high seasonal wind speeds ( Corral et al, 2021 ).…”

“…3) and even possibly yielding negative values (Table 4). Negative values of other ACI constructs coincident with poor R 2 values have previously been attributed to potential effects of giant CCN (Terai et al, 2015;Dadashazar et al, 2017), but further research needs to examine this in more detail.…”

“…Of special interest in this work is the western North Atlantic Ocean (WNAO) where decades of extensive research have been conducted for topics largely unrelated to aerosol–cloud interactions ( Sorooshian et al, 2020 ), thereby providing an opportunity for closing knowledge gaps for this area in a region with a wide range of aerosol and meteorological conditions ( Corral et al, 2021 ; Painemal et al, 2021 ). Past work showed different seasonal cycles of AOD and N d in this region ( Grosvenor et al, 2018 ; Sorooshian et al, 2019 ), which partly motivates this study to unravel why N d behaves differently on seasonal timescales.…”