Clouds in the laboratory: Wind tunnel experiments on collision-coalescence and riming
| Dates: | 1 May 2019 |
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| Times: | 13:00 - 14:00 |
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| What is it: | Seminar |
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| Organiser: | Department of Earth and Environmental Sciences |
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| Who is it for: | University staff, Alumni, Current University students, General public |
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| Speaker: | Dr Jonny Crosier, SEES |
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Since 30 years the Mainz Vertical Wind Tunnel facility is operational for experiments on cloud microphysics and chemistry with emphasis on larger hydrometeors. After the extending the facility for performing experiments down to -30 C processes relevant for mixed phase clouds can be simulated. Recently such experiments to characterize the collision-coalescence process have been conducted for riming and warm-cloud rain formation. Further experiments were dedicated to the investigation of the chemical “retention process” of trace substances (e.g., SO2, H2O2, formaldehyde, several organic acids, and aldehydes , ammonia, HNO3 ,and HCl) during riming on small ice spheres and snow flakes. “Retention” here means the “carry over” of these substances from the initial liquid solution of the "polluted", riming, supercooled droplets onto the frozen hydrometeors. (Some of the materials are returned back to the gas phase –and lost from the hydrometeors- during the freezing process.) The amounts of this retention influence the vertical distribution of the trace gases inside the large convective clouds as well as their “export” through the anvil outflows at high altitudes. This is of relevance for example in the context of the Asian Monsoon Anticyclone where large amounts of trace materials are transported from the boundray layer to high altitudes by deep convective clouds. At first in the presentation several cloud physical processes (like rain formation, freezing, and riming) demonstrated by means of high speed camera video clips. Then an overview of the most recently obtained experimental results is provided together with a discuaaion of their significance.
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G.03
Williamson Building
Manchester
