Abstract
Atmospheric aerosol over the North Atlantic Ocean impacts regional clouds and climate. In this work, we use a set of sun photometer observations of aerosol optical depth (AOD) located on the Graciosa and Cape Verde islands, along with the GEOS‐Chem chemical transport model to investigate the sources of these aerosol and their transport over the North Atlantic Ocean. At both locations, the largest simulated contributor to aerosol extinction is the local source of sea‐salt aerosol. In addition to this large source, we find that signatures consistent with long‐range transport of anthropogenic, biomass burning, and dust emissions are apparent throughout the year at both locations. Model simulations suggest that this signal of long‐range transport in AOD is more apparent at higher elevation locations; the influence of anthropogenic and biomass burning aerosol extinction is particularly pronounced at the height of Pico Mountain, near the Graciosa Island site. Using a machine learning approach, we further show that simulated observations at these three sites (near Graciosa, Pico Mountain, and Cape Verde) can be used to predict the simulated background aerosol imported into cities on the European mainland, particularly during the local winter months, highlighting the utility of background AOD monitoring for understanding downwind air quality.
Highlights
Atmospheric aerosol plays a critical role in the global earth system, strongly impacting climate change, ecosystem function, and human health
We use a set of sun photometer observations of aerosol optical depth (AOD) located on the Graciosa and Cape Verde islands, along with the GEOS‐Chem chemical transport model to investigate the sources of these aerosol and their transport over the North Atlantic Ocean
Model simulations suggest that this signal of long‐range transport in AOD is more apparent at higher elevation locations; the influence of anthropogenic and biomass burning aerosol extinction is pronounced at the height of Pico Mountain, near the Graciosa Island site
Summary
Atmospheric aerosol plays a critical role in the global earth system, strongly impacting climate change, ecosystem function, and human health. Analyses of in situ observations indicate the importance of long‐range transport in the North Atlantic (e.g., Gallo et al, 2020; Zheng et al, 2020); there has been limited exploration and evaluation of model representations of aerosols over this region Constraining this trans‐Atlantic transport is central to characterizing aerosol source contributions to the degradation of air quality over Europe as well as investigating how these aerosol species influence climate and biogeochemistry over the ocean (e.g., Carslaw et al, 2013; Foltz & McPhaden, 2008; Penner et al, 1994). Through a set of simulation experiments, we further investigate the value of these observation sites as predictors imported aerosol to European cities downwind
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