Abstract
This study focuses on the long-term aerosol and precipitation chemistry measurements from colocated monitoring sites in Southern Florida between 2013 and 2018. A positive matrix factorization (PMF) model identified six potential emission sources impacting the study area. The PMF model solution yielded the following source concentration profiles: (i) combustion; (ii) fresh sea salt; (iii) aged sea salt; (iv) secondary sulfate; (v) shipping emissions; and (vi) dust. Based on these results, concentration-weighted trajectory maps were developed to identify sources contributing to the PMF factors. Monthly mean precipitation pH values ranged from 4.98 to 5.58, being positively related to crustal species and negatively related to SO42−. Sea salt dominated wet deposition volume-weighted concentrations year-round without much variability in its mass fraction in contrast to stronger seasonal changes in PM2.5 composition where fresh sea salt was far less influential. The highest mean annual deposition fluxes were attributed to Cl−, NO3−, SO42−, and Na+ between April and October. Nitrate is strongly correlated with dust constituents (unlike sea salt) in precipitation samples, indicative of efficient partitioning to dust. Interrelationships between precipitation chemistry and aerosol species based on long-term surface data provide insight into aerosol–cloud–precipitation interactions.
Highlights
IntroductionFew studies focusing on Aerosol–cloud interactions (ACI) over the Western North Atlantic Ocean (WNAO) have primarily relied on ship and/or aircraft data [8]
Aerosol–cloud interactions (ACI) are complex and not accurately represented by climate models [1].These interactions remain the largest source of uncertainty in anthropogenic radiative forcing [2,3].In contrast to subtropical regions characterized by stratocumulus decks such as off the western coasts of the United States (U.S.) [4], Chile [5], and Southern Africa (e.g., [6,7]), marine-related ACI studies are more scarce over the Western North Atlantic Ocean (WNAO) region [8]. few studies focusing on ACI over the WNAO have primarily relied on ship and/or aircraft data [8]
Low monthly variability in soil moisture may be related to precipitation occurring throughout the year (Figure 2d) and the fact that the site is located over a shallow aquifer [58]
Summary
Few studies focusing on ACI over the WNAO have primarily relied on ship and/or aircraft data [8] Even though these efforts have, in some cases, provided data at high temporal and spatial resolution and in the vicinity of clouds, downsides are the high cost, challenging logistics, and statistical limitations innate to short-term intensive campaigns. An alternative and indirect method to gain inferences about ACI is to use long-term data at surface monitoring networks gathering compositional data for precipitation and particulate matter. This method has been demonstrated for other regions such as an inland California site [9], the Southwestern U.S [10], and Mexico City [11]
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