Abstract
Abstract. To quantify the contribution of new particle formation (NPF) to ultrafine particle number and cloud condensation nuclei (CCN) budgets, one has to understand the mechanisms that govern NPF in different environments and its temporal extent. Here, we study NPF in Cyprus, an Eastern Mediterranean country located at the crossroads of three continents and affected by diverse air masses originating from continental, maritime, and desert-dust source areas. We performed 1-year continuous measurements of aerosol particles down to ∼ 1 nm in diameter for the first time in the Eastern Mediterranean and Middle East (EMME) region. These measurements were complemented with trace gas data, meteorological variables, and retroplume analysis. We show that NPF is a very frequent phenomenon at this site and has higher frequencies of occurrence during spring and autumn. NPF events were both of local and regional origin, and the local events occurred frequently during the month with the lowest NPF frequency. Some NPF events exhibited multiple onsets, while others exhibited apparent particle shrinkage in size. Additionally, NPF events were observed during the nighttime and during episodes of high desert-dust loadings. Particle formation rates and growth rates were comparable to those in urban environments, although our site is a rural one. Meteorological variables and trace gases played a role in explaining the intra-monthly variability of NPF events, but they did not explain why summer months had the least NPF frequency. Similarly, pre-existing aerosol loading did not explain the observed seasonality. The months with the least NPF frequency were associated with higher H2SO4 concentrations but lower NO2 concentrations, which is an indicator of anthropogenic influence. Air masses arriving from the Middle East were not observed during these months, which could suggest that precursor vapors important for nucleation and growth are transported to our site from the Middle East. Further comprehensive measurements of precursor vapors are required to prove this hypothesis.
Highlights
Atmospheric new particle formation (NPF) is the process by which oxidized precursor gases initially form molecular clusters that further grow in size by multi-component condensation (Kulmala et al, 2014)
In the course of identifying NPF events, the particle size distribution (PSD) spectrum is usually analyzed, mainly at sizes below 25 nm where one can detect the emergence of new aerosol particles, and the particle growth to larger sizes is followed
We mainly focus on daytime data having global radiation > 50 W m−2 as this is the time period relevant for most NPF events, but we briefly mention some nighttime events
Summary
Atmospheric new particle formation (NPF) is the process by which oxidized precursor gases initially form molecular clusters that further grow in size by multi-component condensation (Kulmala et al, 2014). R. Baalbaki et al.: Towards understanding the characteristics of new particle formation studies have focused on this phenomenon over the past 2 decades, because it is a large source of the global aerosol particle number and cloud condensation nuclei (CCN) load (Gordon et al, 2017; Merikanto et al, 2009; Pierce and Adams, 2009; Wang and Penner, 2009; Yu and Luo, 2009; Kerminen et al, 2012; Spracklen et al, 2006, 2008). The collective scientific outcome from these studies is essential to understand the mechanisms and characteristics of NPF (Kerminen et al, 2018; Lee et al, 2019; Chu et al, 2019) and how it affects the global climate (e.g., Spracklen et al, 2006; Gordon et al, 2017)
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