Nocturnal new particle formation events in urban environments
Few studies have investigated nocturnal new particle formation (NPF) events, and none of them were conducted in urban environments. Nocturnal NPF can potentially be a significant source of particles in urban areas, and studying them would improve our understanding of nucleation mechanisms. To addres...
| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2017-01-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | http://www.atmos-chem-phys.net/17/521/2017/acp-17-521-2017.pdf |
| Summary: | Few studies have investigated nocturnal new particle formation
(NPF) events, and none of them were conducted in urban environments.
Nocturnal NPF can potentially be a significant source of particles in urban
areas, and studying them would improve our understanding of nucleation
mechanisms. To address this, our study was conducted in an urban environment
to investigate the physical characteristics of NPF events, with a particular
focus on nocturnal events and the differences between them and the daytime
NPF events. Particle number size distribution (PNSD) was measured for 2 weeks at each of 25 sites across an urban environment. A new method was
proposed to automatically categorise NPF events based on growth rate (GR) in
order to remove the bias related to the manual procedure. Out of 219
observed events, 118 and 101 were categorised into class I and II
respectively and 73 happened during the nighttime which included more than
30 % of the events. GR and condensation sink (CS) were calculated and a
slight negative relationship between GR and CS was observed. Nocturnal
events displayed higher GRs compared to daylight ones which were on average
about 10 %. Back trajectory analysis was also conducted to estimate the
locations of the sources of daylight and nocturnal precursors. While the
precursors related to daylight events originated from different locations
with no particular pattern, back-trajectory analysis showed many air masses
associated with nocturnal NPF events were transported from over the ocean.
Overall, nocturnal NPF events were found to be a significant source of
particles in the studied environment with different physical
characteristics and/or sources compared to daylight events. |
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| ISSN: | 1680-7316 1680-7324 |