Vertical and horizontal distribution of regional new particle formation events in Madrid

Abstract

Abstract. The vertical profile of new particle formation (NPF) events was studied by comparing the aerosol size number distributions measured aloft and at surface level in a suburban environment in Madrid, Spain, using airborne instruments. The horizontal distribution and regional impact of the NPF events was investigated with data from three urban, urban background, and suburban stations in the Madrid metropolitan area. Intensive regional NPF episodes followed by particle growth were simultaneously recorded at three stations in and around Madrid during a field campaign in July 2016. The urban stations presented larger formation rates compared to the suburban station. Condensation and coagulation sinks followed a similar evolution at all stations, with higher values at urban stations. However, the total number concentration of particles larger than 2.5 nm was lower at the urban station and peaked around noon, when black carbon (BC) levels are at a minimum. The vertical soundings demonstrated that ultrafine particles (UFPs) are formed exclusively inside the mixed layer. As convection becomes more effective and the mixed layer grows, UFPs are detected at higher levels. The morning soundings revealed the presence of a residual layer in the upper levels in which aged particles (nucleated and grown on previous days) prevail. The particles in this layer also grow in size, with growth rates significantly smaller than those inside the mixed layer. Under conditions with strong enough convection, the soundings revealed homogeneous number size distributions and growth rates at all altitudes, which follow the same evolution at the other stations considered in this study. This indicates that UFPs are detected quasi-homogenously in an area spanning at least 17 km horizontally. The NPF events extend over the full vertical extension of the mixed layer, which can reach as high as 3000 m in the area, according to previous studies. On some days a marked decline in particle size (shrinkage) was observed in the afternoon, associated with a change in air masses. Additionally, a few nocturnal nucleation-mode bursts were observed at the urban stations, for which further research is needed to elucidate their origin.

Synergistic effect of the occurrence of African dust outbreaks on atmospheric pollutant levels in the Madrid metropolitan area

“…In the Madrid metropolitan area the main local source of primary UFP is traffic (Brines et al, 2015). In the summer period, UFP generated by nucleations can also appear at the regional scale (Carnerero et al, 2018). The nucleation precursor gases can be anthropogenic and biogenic.…”

New particle formation at urban and high-altitude remote sites in the south-eastern Iberian Peninsula

“…Due to the role of NPF in the production of CCN, it is of special interest to characterise NPF in the free troposphere (FT) and its vertical distribution. However, only a few studies have focused on the vertical distribution of these events (e.g., Carnerero et al, 2018;Komppula et al, 2003) and the existing observations of NPF at high altitudes provide contradictory results. For example, Crumeyrolle et al (2010) showed that the occurrence of NPF events was limited to the planetary boundary layer (PBL), while Hamburger et al (2011) have reported the presence of high concentrations of ultrafine particles in the upper FT, and Boulon et al (2011) found that the nucleation processes were more frequent in a high-altitude site than in the PBL, due to enhanced ion contribution to NPF at high altitudes.…”

Analysis of summer O<sub>3</sub> in the Madrid air basin with the LOTOS-EUROS chemical transport model

“…Regional CTMs have been used to investigate O 3 pollution in Spain in several studies. Most of these studies aimed to describe short-term (rarely exceeding 5 d) pollution events (Toll and Baldasano, 2000;Jiménez et al, 2005Jiménez et al, , 2006San José et al, 2005;Carvalho et al, 2006;Valverde et al, 2016;Pay et al, 2018) and, in some cases, to discuss the effectiveness of potential mitigation strategies (Palacios et al, 2002;Soret et al, 2014). Despite these efforts, work is still needed to evaluate the impact of changes in the vertical configuration of CTMs, especially in the Mediterranean region where the atmospheric dynamics in summer is characterised by complex recirculation processes with effective vertical exchange (Millán et al, 1997(Millán et al, , 2000Gangoiti et al, 2001;Borge et al, 2010;Querol et al, 2017Querol et al, , 2018.…”

“…In the Iberian Peninsula, the use of fine grids (in the order of 1-5 km× 1-5 km) has been found to be beneficial in the context of complex terrains where mesoscale processes acquire importance for interpreting production and transport of O 3 (Toll and Baldasano, 2000;Jiménez-Guerrero et al, 2008). In coastal areas, with complex topography, high-resolution simulations have been generally employed with good results (Carvalho et al, 2006;Jiménez et al, 2006;Gonçalves et al, 2009). Moreover fine grids have been recommended for describing O 3 variability especially in urban and industrial areas (Jiménez et al, 2006;Baldasano et al, 2011).…”

“…In complex domains in the Iberian Peninsula the models may not reproduce O 3 concentrations due to a poor representation of mesoscale flows and layering and accumulation of pollutants (Gonçalves et al, 2009). In general, it has been demonstrated that incrementing vertical resolution would help to resolve meteorological phenomena (Carvalho et al, 2006) and would also offer a more realistic vertical exchange between the boundary layer and the free troposphere (Jiménez et al, 2006).…”