1Leibniz Institute for Tropospheric Research, 04318 Leipzig, Germany
2RIVM - National Institute for Public Health and the Environment, 3720 BA Bilthoven, The Netherlands
3Department of Physics, Michigan Technological University, Houghton, MI 49931, USA
4Department of Physics, University of Helsinki, P.O. Box 64, 00014 Helsinki, Finland
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.