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Title:
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A high-flow turbulent cloud chamber
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Author(s):
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Published by:
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Publication date:
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ECN
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1995
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ECN report number:
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Document type:
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ECN-RX--95-004
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Other
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Number of pages:
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Full text:
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20
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Download PDF
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Abstract:
A large laboratory facility (cloud chamber) has been built to study cloudformation under reproducible conditions. The chamber is designed to assess
the influence of anthropogenic aerosols on the microstructure of marine
clouds in coastal Western Europe. For this reason the supersaturations in the
chamber are low, in the order of 0.1%, typical for coastal marine stratus.
The very large size (30 m3) and flow (30 m3/min) of the chamber allow
unperturbed use of conventional cloud instrumentation like Forward Scattering
Spectrometer Probe (TSI Inc.) and high-flow cascade impactors for chemical
analysis of aerosol and droplets. The performance of the cloud chamber was
tested with laboratory-generated submicron-sized ammonium sulfate aerosol
with a lognormal size distribution and varying the number concentrations. It
was found that the sulfate particles above a threshold size of 0.07
micrometer in diameter grew into droplets (became 'activated'), which
corresponds according to the Kohler theory to supersaturation of 0.15%.
Estimates of the maximum supersaturation in the chamber from the measured LWC
(liquid water content) gives the same value. Tests show that LWC, droplet
spectra and activation threshold are stable for hours and reproducible from
day to day. 6 figs., 20 refs.
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