Characterization of Urban New Particle Formation in Amman—Jordan

Abstract

We characterized new particle formation (NPF) events in the urban background of Amman during August 2016–July 2017. The monthly mean of submicron particle number concentration was 1.2 × 104–3.7 × 104 cm−3 (exhibited seasonal, weekly, and diurnal variation). Nucleation mode (10–15 nm) concentration was 0.7 × 103–1.1 × 103 cm−3 during daytime with a sharp peak (1.1 × 103–1.8 × 103 cm−3) around noon. We identified 110 NPF events (≈34% of all days) of which 55 showed a decreasing mode diameter after growth. The NPF event occurrence was higher in summer than in winter, and events were accompanied with air mass back trajectories crossing over the Eastern Mediterranean. The mean nucleation rate (J10) was 1.9 ± 1.1 cm−3 s−1 (monthly mean 1.6–2.7 cm−3 s−1) and the mean growth rate was 6.8 ± 3.1 nm/h (4.1–8.8 nm/h). The formation rate did not have a seasonal pattern, but the growth rate had a seasonal variation (maximum around August and minimum in winter). The mean condensable vapor source rate was 4.1 ± 2.2 × 105 molecules/cm3 s (2.6–6.9 × 105 molecules/cm3 s) with a seasonal pattern (maximum around August). The mean condensation sink was 8.9 ± 3.3 × 10−3 s−1 (6.4–14.8 × 10−3 s−1) with a seasonal pattern (minimum around June and maximum in winter).

Regional New Particle Formation over the Eastern Mediterranean and Middle East

“…The station exhibits urban characteristics, since 40% of the total population of Jordan lives in Amman. More details concerning the Amman measuring site can be found in [12].…”

“…Finally, a NanoScan SMPS (TSI Model 3910) measured PNSDs every 60 s in Amman, in the 10-420 nm range (13 size bins). The PNSD raw data were 5 min-averaged and more details can be found in [12]. The system used at Finokalia is part of the ACTRIS network (Aerosol, Clouds, and Trace gases Research Infrastructure) and has successfully passed intercomparison tests in 2013 and 2016 [19], while the instrument in Amman was calibrated by the manufacturer prior to the onset of the campaign (June 2016).…”

“…Comparable results can be found over the Scandinavian Peninsula [7]; strong NPF events recorded in Southern and Northern Finland (Hyytiälä and Värriö, respectively), occurred within a spatial scale of 220 km reflecting thus the regional character of NPF. In a study conducted in Amman (Jordan) [12], high probability of NPF was reported when air masses cross over the Eastern Mediterranean reflecting the potential regionality of the phenomenon as part of largerscale NPF process. In Greece, initial indications on regional-scale NPF phenomena have been observed at two coastal sites (within a distance of 120 km) located in the Aegean Sea (AS) during July 2013 [9].…”

“…The current work follows up on the initial assessment in Greece by [10], using a subset of the data analyzed in Greece and Jordan that covers a common period [10,12], and discusses the homogeneity of NPF events at an even larger, regional scale. Hence, we aim to (i) identify common events between Athens, Finokalia and Amman, locations separated by almost 1300 km, (ii) examine the processes and dynamic characteristics (e.g., formation and growth rates) leading to concurrent NPF at all the three stations and (iii) explore the essential role of meteorology via the air masses path arriving at the stations throughout NPF event days.…”

Observations of new particle formation, modal growth rates, and direct emissions of sub-10 nm particles in an urban environment

“…The atmospheric condensation sink, which is dependent on the pre-existing aerosol concentration, plays a key role in the occurrence of NPF events ( Dal Maso, 2002 ). By acting as a sink for volatile compounds and small clusters, a high pre-existing aerosol load can hinder NPF ( Hussein et al, 2020 ; Salma et al, 2016 ; Z. B.…”