Abstract
Abstract. New particle formation has been observed at a number of ground-based measurement sites. Prior research has provided evidence that this new particle formation, while observed in the near-surface layer, is actually occurring in atmospheric layers above the surface and appears to be focused in or close to the residual layer formed by the nocturnal inversion. Here, we present both observations and modeling for southern Indiana which support this postulate. Based on simulations with a detailed aerosol dynamics model and the Weather Research and Forecasting model, along with data from ground-based remote sensing instruments and detailed gas and particle phase measurements, we show evidence that (i) the maximum rate change of ultrafine particle concentrations as observed close to the surface is always preceded by breakdown of the nocturnal inversion and enhancement of vertical mixing and (ii) simulated particle size distributions exhibit greatest accord with surface observations during and subsequent to nucleation only when initialized with a particle size distribution representative of clear atmospheric conditions, rather than the in situ (ground-level) particle size distribution.
Highlights
Introduction and objectivesParticle nucleation has been observed with high frequency at a geographically diverse suite of ground-based measurement sites (Kulmala et al, 2011) and plays a key role in determining the ambient particle size distribution (Spracklen et al., 2006), but the controls and limitations on nucleation occurrence and growth remain uncertain
Balloon-borne observations during the SATURN experiment near Leipzig in Germany provided evidence that prior to the break-up of the nocturnal inversion nucleation was focused on the residual layer and, subsequent to erosion of the inversion and growth of the boundary layer, nucleation was observed throughout the planetary boundary layer (Stratmann et al, 2003; Wehner et al, 2007)
Turbulence intensity as measured with the ZephIR lidar indicates a strong link between the occurrence of high concentrations of ultra-fine particles at the Morgan Monroe State Forest (MMSF) site and boundary layer dynamics
Summary
Particle nucleation has been observed with high frequency at a geographically diverse suite of ground-based measurement sites (Kulmala et al, 2011) and plays a key role in determining the ambient particle size distribution (Spracklen et al., 2006), but the controls and limitations on nucleation occurrence and growth remain uncertain. Balloon-borne observations during the SATURN experiment near Leipzig in Germany provided evidence that prior to the break-up of the nocturnal inversion nucleation was focused on the residual layer and, subsequent to erosion of the inversion and growth of the boundary layer, nucleation was observed throughout the planetary boundary layer (Stratmann et al, 2003; Wehner et al, 2007). In that research vertical profiles of particle size distributions were taken in a helicopter borne package and the evolution of the boundary layer was observed using a lidar
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