 |
| Titel |
Multiple daytime nucleation events in semi-clean savannah and industrial environments in South Africa: analysis based on observations |
| VerfasserIn |
A. Hirsikko, V. Vakkari, P. Tiitta, J. Hatakka, V.-M. Kerminen, A.-M. Sundström, J. P. Beukes, H. E. Manninen, M. Kulmala  , L. Laakso |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1680-7316
|
| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 13, no. 11 ; Nr. 13, no. 11 (2013-06-06), S.5523-5532 |
| Datensatznummer |
250018686
|
| Publikation (Nr.) |
 copernicus.org/acp-13-5523-2013.pdf |
|
|
|
|
|
| Zusammenfassung |
| Recent studies have shown very high frequencies of atmospheric new particle
formation in different environments in South Africa. Our aim here was to
investigate the causes for two or three consecutive daytime nucleation
events, followed by subsequent particle growth during the same day. We
analysed 108 and 31 such days observed in a polluted industrial and
moderately polluted rural environments, respectively, in South Africa. The
analysis was based on two years of measurements at each site. After rejecting
the days having notable changes in the air mass origin or local wind
direction, i.e. two major reasons for observed multiple nucleation events,
we were able to investigate other factors causing this phenomenon. Clouds
were present during, or in between most of the analysed multiple particle
formation events. Therefore, some of these events may have been single
events, interrupted somehow by the presence of clouds. From further analysis,
we propose that the first nucleation and growth event of the day was often
associated with the mixing of a residual air layer rich in SO2 (oxidized
to sulphuric acid) into the shallow surface-coupled layer. The second
nucleation and growth event of the day usually started before midday and was
sometimes associated with renewed SO2 emissions from industrial origin.
However, it was also evident that vapours other than sulphuric acid were
required for the particle growth during both events. This was especially the
case when two simultaneously growing particle modes were observed. Based on
our analysis, we conclude that the relative contributions of estimated
H2SO4 and other vapours on the first and second nucleation and
growth events of the day varied from day to day, depending on anthropogenic
and natural emissions, as well as atmospheric conditions. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|