Abstract
Abstract. Aerosol particle measurements in the atmospheric boundary layer performed by a helicopter-borne measurement payload and by a lidar system from a case study during the IMPACT field campaign in Cabauw (NL) are presented. Layers of increased number concentrations of ultrafine particles were observed in the residual layer, indicating relatively recent new-particle formation. These layers were characterized by a sub-critical Richardson number and concomitant increased turbulence. Turbulent mixing is likely to lead to local supersaturation of possible precursor gases which are essential for new particle formation. Observed peaks in the number concentrations of ultrafine particles at ground level are connected to the new particle formation in the residual layer by boundary layer development and vertical mixing.
Highlights
New particle formation (NPF) in the size range of a few nanometers in diameter, has been observed in the atmosphere at various locations: urban, remote, and arctic sites (e.g., Stanier et al, 2004; Weber et al, 1997; Wiedensohler et al, 1996). Kulmala et al (2004) reviewed more than 100 of such experimental studies from worldwide locations concluding that NPF was found under a wide range of atmospheric conditions almost everywhere on the globe where it was looked for
Layers of increased number concentrations of ultrafine particles were observed in the residual layer, indicating relatively recent new-particle formation
Turbulent mixing is likely to lead to local supersaturation of possible precursor gases which are essential for new particle formation
Summary
New particle formation (NPF) in the size range of a few nanometers in diameter, has been observed in the atmosphere at various locations: urban, remote, and arctic sites (e.g., Stanier et al, 2004; Weber et al, 1997; Wiedensohler et al, 1996). Kulmala et al (2004) reviewed more than 100 of such experimental studies from worldwide locations concluding that NPF was found under a wide range of atmospheric conditions almost everywhere on the globe where it was looked for. Increased number concentrations of ultrafine particles were observed after break-up of the nocturnal inversion within the whole mixed layer (Stratmann et al, 2003) and near the inversion correlating well with high fluctuations of the temperature and humidity caused by plumes penetrating the inversion (Siebert et al, 2004). Such penetration caused intensive mixing, which in turn apparently significantly increased nucleation and growth rates. The presented combination of helicopter flights and lidar measurements is unique and helps to understand the potential connection between particle formation and growth and boundary layer development
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