Regional effect on urban atmospheric nucleation

Abstract

Secondary aerosol particle production via new particle formation (NPF) has been shown to be a major contributor to the global aerosol load. NPF has also been observed frequently in urban environments. Here, we investigate the effect of regional NPF on urban aerosol load under well-defined atmospheric conditions. The Carpathian Basin, the largest orogenic basin in Europe, represents an excellent opportunity for exploring these interactions. Based on longterm observations, we revealed that NPF seen in a central large city of the basin (Budapest) and its regional background occur in a consistent and spatially coherent way as a result of a joint atmospheric phenomenon taking place on large horizontal scales. We found that NPF events at the urban site are usually delayed by > 1 h relative to the rural site or even inhibited above a critical condensational sink level. The urban processes require higher formation rates and growth rates to be realized, by mean factors of 2 and 1.6, respectively, than the regional events. Regional-and urban-type NPF events sometimes occur jointly with multiple onsets, while they often exhibit dynamic and timing properties which are different for these two event types.

Quantification of an atmospheric nucleation and growth process as a single source of aerosol particles in a city

“…The diurnal patterns represented by Fig. 2 are coherent with previous ideas on the NPF and growth events in the Budapest area (Salma et al, 2014(Salma et al, , 2016b. They also confirm the basic assumptions of the NSF NUC definition about the source intensities at both location types.…”

“…It is seen that the NPF frequency has an obvious seasonal variation. This can be obtained from its monthly dependency, which exhibits an absolute and local minimum in January and August, respectively, and an absolute and local maximum in March or April, and September, respectively (Salma et al, 2016b). The seasonal variation of the nucleation frequency fits into the second group of measurement sites -which is characterized by the highest number of nucleation events in spring and the lowest in winter, with a relatively high total number of events (Manninen et al, 2010).…”

“…New particle formation has also been proven to be common in large cities (Nieminen et al, 2017). Urban NPF can interact with and can be influenced by regional nucleation events, at least under some geographic conditions, and can become part of a phenomenon with a much larger horizontal extension than the city (Salma et al, 2016b). At the same time, particle number concentrations in cities are strongly affected by high-temperature emission sources from different sectors (Paasonen et al, 2016) such as household and residential heating (e.g.…”

Long-term analysis of clear-sky new particle formation events and nonevents in Hyytiälä

“…The association of a high CS with the lower NPF probability has been observed in many studies conducted in Hyytiälä (Boy and Kulmala, 2002;Hyvönen et al, 2005;Baranizadeh et al, 2014), as well as in other rural and urban areas, including Egbert and Toronto in Canada (Jun et al, 2014), Preila in Lithuania (Mordas et al, 2016), Po Valley in Italy (Hamed et al, 2007) and Budapest and K-puszta in Hungary (Salma et al, 2016).…”

“…During the last couple of decades, NPF has been observed to take place almost all over the world (Kulmala et al, 2004a;Zhang et al, 2011;Bianchi et al, 2016;Kontkanen et al, 2016aKontkanen et al, , 2017. Atmospheric NPF is thought to be the dominant source of the total particle number concentration ) and a major source of cloud condensation nuclei in the global tro-posphere (Merikanto et al, 2009;Yu et al, 2010;Kerminen et al, 2012;Salma et al, 2016).…”