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Vertical transport of accumulation mode particles between two street canyons and the urban boundary layer

 
: Salmond, J.A.; Pauscher, L.; Pigeon, G.; Masson, V.; Legain, D.

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Atmospheric environment 44 (2010), 39, pp.5139-5147
ISSN: 0004-6981
ISSN: 1352-2310
English
Journal Article
Fraunhofer IWES ()
turbulent fluxes; accumulation mode particles; urban canopy layer; urban boundary layer; particle fluxes

Abstract
Concentrations and turbulent fluxes of accumulation mode particles were measured during the 2004–2005 ‘Canopy and Aerosol Particle Interaction in Toulouse Urban Layer’ project (CAPITOUL) at the top of two intersecting street canyons and in the urban boundary layer (UBL) in Toulouse, France. Particle numbers were strongly affected by boundary layer depth and showed limited sensitivity to local emissions. Differences in the diurnal patterns of particle numbers were observed between the finer fraction (0.3–0.4 μm) and coarser fraction (1.6–2.0 μm) of accumulation mode particles, indicating different processes of formation, evolution and transportation may be dominant. Highest particle numbers were observed in the narrow street canyon which had more limited local emissions and comparatively small particle fluxes. However, the improved ventilation rate in the wider canyon was also associated with the downward mixing of particles into the street canyon from the UBL. The results from this study clearly illustrate the temporal and spatial variability of particle numbers and fluxes in the urban atmosphere.

: http://publica.fraunhofer.de/documents/N-410589.html