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Vertical profiles of sub-3 nm particles over the boreal forest
This work presents airborne observations of sub3 nm particles in the lower troposphere and investigates new particle formation (NPF) within an evolving boundary layer (BL). We studied particle concentrations together with supporting gas and meteorological data inside the planetary BL over a boreal f...
Autores principales: | , , , , , , , , , , , , , , , , , , , , , , |
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Lenguaje: | eng |
Publicado: |
2019
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Materias: | |
Acceso en línea: | https://dx.doi.org/10.5194/acp-19-4127-2019 http://cds.cern.ch/record/2805300 |
Sumario: | This work presents airborne observations of sub3 nm particles in the lower troposphere and investigates new
particle formation (NPF) within an evolving boundary layer
(BL). We studied particle concentrations together with supporting gas and meteorological data inside the planetary BL
over a boreal forest site in Hyytiälä, southern Finland. The
analysed data were collected during three flight measurement campaigns: May–June 2015, August 2015 and April–
May 2017, including 27 morning and 26 afternoon vertical profiles. As a platform for the instrumentation, we used
a Cessna 172 aircraft. The analysed flight data were collected horizontally within a 30 km distance from SMEAR
II in Hyytiälä and vertically from 100 m above ground level
up to 2700 m. The number concentration of 1.5–3 nm particles was observed to be, on average, the highest near the
forest canopy top and to decrease with increasing altitude
during the mornings of NPF event days. This indicates that
the precursor vapours emitted by the forest play a key role
in NPF in Hyytiälä. During daytime, newly formed particles
were observed to grow in size and the particle population
became more homogenous within the well-mixed BL in the
afternoon. During undefined days with respect to NPF, we
also detected an increase in concentration of 1.5–3 nm particles in the morning but not their growth in size, which indicates an interrupted NPF process during these undefined
days. Vertical mixing was typically stronger during the NPF
event days than during the undefined or non-event days. The
results shed light on the connection between boundary layer
dynamics and NPF. |
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