One-year measurement of size-resolved particle fluxes in an urban area

Abstract

Size-resolved particle flux measurements were carried out in an urban area from April 2012 to April 2013. Together with a standard eddy covariance system, two fast optical particle counters have been employed on a 65-meter-high tower in Mu¨nster, Germany. Particle number fluxes were directly calculated for particles with diameters from 0.06 to 10 mm within 16 individual size-bins. Whereas particle number concentrations show a distinct yearly pattern with maxima in winter and minima in summer, the flux time series is more multifaceted. Average daily maxima of 3.0e'07 particles m (2 s (1 occurred during winter while minima of 2.0e'06 particles m (2 s (1 were observed in fall. The size-resolved measurements revealed that during spring and summer a considerable number of accumulation mode particles deposits while a simultaneous net particle emission occurred, which is mostly driven by particles smaller than 0.12 mm. These bi-directional fluxes lead to a net mass deposition of up to 13.5 mg m (2 d (1 . The tipping-point between the emission and deposition lay between 0.16 and 0.19 mm. In a comprehensive analysis of the flux and concentration time series, the degree of atmospheric stability, the seasons, and the type of source region have been identified as key influences for particle fluxes. Different responses between particle fluxes and concentrations have been found along these drivers.

Dissimilarity Between Dust, Heat, and Momentum Turbulent Transports During Aeolian Soil Erosion

“…Most studies having measured particle flux from this technique focused on the quantification of the flux itself and not on its analogy with momentum or heat fluxes. These studies were mainly performed over urban areas (Deventer, El‐Madany, et al, ; Dorsey et al, ; Ma˙rtensson et al, ), vegetated surfaces (Damay et al, ; Deventer, Held, et al, ), and much less over desert areas (Fratini et al, ; Porch & Gillette, ). The only studies comparing particle and heat turbulent transports either observed similarity between both scalars (Fratini et al, ; Ma˙rtensson et al, ) or assumed similarity to correct their particle flux from the heat flux due to the slow response time of their particle counter (Damay et al, ; Deventer, Held, et al, ).…”

Acceleration of the condensational growth of water droplets in an external electric field

“…We expect to develop further understanding of droplet growth mechanisms in natural clouds and fog. For example, the observation of bidirectional fluxes in fog lead to new questions of temporal limitations of droplet growth and evaporation mechanisms [71][72]. It is not unlikely that these bidirectional fluxes of microdroplets can be supported by electric fields that are typically present near the Earth's surface [11,70].…”

Review and Integration of Biosphere-Atmosphere Modelling of Reactive Trace Gases and Volatile Aerosols

“…Initially, measurements were made with fast laser-based optical particle spectrometers, typically covering the size range 0.1-1 μm Nemitz et al 2002;Sievering 1983Sievering , 1987) and more recently 0.25-2.5 μm (Ahlm et al 2010;Vogt et al 2011) and down to 0.06 μm (Deventer et al 2011;Harrison et al 2011). A range of aerodynamic and electromobility spectrometers have also now been used (Damay et al 2009;Grönholm et al 2007;Nemitz et al 2000a;Pryor 2006;Pryor et al 2009;Schmidt and Klemm 2008).…”

“…Urban flux measurements represent the emission from combustion sources and (wind-driven and vehicle induced) resuspension (Deventer et al 2011;Dorsey et al 2002;Järvi et al 2009;Martin et al 2008;Schmidt and Klemm 2008;Vogt et al 2011). There are clearly situations in which emissions take place.…”