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Snowflakes

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18:30 – 18:30 9 Dec 2009
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Lancaster University, Bailrigg, Lancaster, UK LA1 4YW

Speakers: Dr Paul Connolly

The physics of water in its solid phase leads to the spectacular variety of forms that are seen in snowflakes. They begin as snow crystals, which develop when tiny supercooled cloud droplets (about 10 μm in diameter) freeze. Come to this talk to learn more about them.
Abstract
In atmospheric clouds at temperatures below -35C spontaneous freezing gives copious ice particles, but at higher temperatures relatively few ice crystals form and clouds typically consist of supercooled water drops. Recent research has found that the number 1 uncertain parameter in determining the climates sensitivity to a doubling of CO2 is the fall speed of snow in atmospheric clouds.
The fall speeds depend strongly on how efficiently ice crystals can stick together upon colliding (aggregate). Studying ice aggregation is difficult, owing to dependence on several variables (ice particle size, temperature, number concentration, shape). Our new Manchester Ice Cloud Chamber includes state-of-the-art microphysical instrumentation to study ice formation and aggregation in supercooled clouds. It consists of three large cold rooms joined by a 10m tall particle fall tube (1m diameter) in which ice cloud properties and ice crystal growth can be studied over much longer time scales than was possible using smaller chambers.
The temperature in each room is separately controlled down to -50C and it is possible to close off sections of the fall tube if smaller scale experiments are required. The first examples of experiments performed with the MICC and model calculations to show the applicability to the atmosphere will be presented.
The meeting is open to all. Light refreshments will be available from 18:00. The Faraday Building is no. 22 on the campus map www.lancs.ac.uk/travel/images/campus.pdf
Parking can be found by the Chaplaincy (no 20) adjacent to “Reception” with access through Bowland College (no 23). Parking is free after 18:00.

Event type: Lecture/Talk
Organised by: Lancashire and Cumbria Branch
Contact details: Dr John Bradshaw
john.bradshaw@physics.org

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Lancaster University, Bailrigg, Lancaster, UK LA1 4YW
Clock icon
18:30 – 18:30 9 Dec 2009
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Invite friends
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