ECN publication
A high-flow turbulent cloud chamber
Published by: Publication date:
ECN 1995
ECN report number: Document type:
ECN-RX--95-004 Other
Number of pages: Full text:
20 Download PDF  

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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