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SUMMARY:The aerosol indirect effect in mixed phase and ice clouds - Tom Ch
 oularton\, The University of Manchester
DTSTART:20081111T110000Z
DTEND:20081111T120000Z
UID:TALK14930@talks.cam.ac.uk
CONTACT:11354
DESCRIPTION:Detailed ground based studies of the initiation of the ice pha
 se in clouds enveloping the Jungfraujoch in the Swiss Alps will be describ
 ed. It is shown that a higher concentration of ice crystals is found in cl
 ouds forming in polluted air. The evidence is that these ice crystals are 
 associated with carbonaceous aerosol. The origin and development of this a
 erosol is described. Another feature observed in these clouds\, and also i
 n layer clouds more generally\, is that in mixed phase clouds fully glacia
 ted regions are found in close proximity to regions consisting largely of 
 supercooled water.\n\nFinally the influence of pollution aerosol on the ex
 tent and ice microphysics of anvil cirrus forming above deep tropical conv
 ection observed during the ACTIVE programme will be discussed. It is found
  that the number of available cloud condensation nuclei can modulate the l
 oading of supercooled water entering the homogeneous freezing zone. The su
 dden freezing of this water releases latent heat of fusion\, which can inc
 rease the height of cloud top and the amount of water available to the anv
 il cloud. Further haze freezing appears to be an important source of ice c
 rystals in anvil regions away from the main cloud updraft.\n
LOCATION:British Antarctic Survey\, Room 307
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