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SUMMARY:Influence of Aerosol Chemical Composition and Size on Heterogeneou
 s Ice Formation under Mid-Upper Troposphere Conditions
DTSTART:20110721T091500
DTSTAMP:20260427T214928Z
UID:e486e9b4f88f56165f1d55b854915ab176af414578c53bbf1cfde50a
CATEGORIES:Conferences - Seminars
DESCRIPTION:Zaminhussein Kanji\nAtmospheric aerosols play a pivotal role i
 n climate and air quality. One key uncertainty in predicting future climat
 e is the contribution of various chemical and physical processes to the ra
 diative balance of the Earth. In particular  the physical properties of ae
 rosols such as size and solubility and chemical properties such as surface
 /bulk reactivity resulting in chemical composition changes. Depending on t
 hese properties  aerosols are involved in cooling/warming the atmosphere d
 irectly via interaction with incoming solar radiation (aerosol direct effe
 ct)  or via their ability to act as cloud condensation or ice nuclei and t
 hus play a role in cloud formation (indirect effect). Ice nuclei are parti
 cles that trigger ice formation on their surface either directly from the 
 vapour or liquid phase (heterogeneous ice nucleation). \n \nThe current wo
 rk addresses how the chemical composition and size/surface area of various
  tropospherically relevant aerosols influence conditions of temperature (T
 ) and relative humidity (RH) required for heterogeneous ice formation cond
 itions in the mid-upper troposphere regime (253 – 220K)? Motivation for 
 this comes first  the importance of being able to predict ice formation ac
 curately so as to understand the hydrological cycle since the ice is the p
 rimary initiator of precipitation forming clouds. Second  the tropospheric
  budget of water vapour  an especially active greenhouse gas is strongly i
 nfluenced by ice nucleation and growth. Third  ice surfaces in the atmosph
 ere act as heterogeneous surfaces for chemical reactions of trace gases (e
 .g.  SO2  O3  NOx) and therefore being able to accurately estimate ice for
 mation rates and quantify ice surface concentrations will allow a more acc
 urate calculation of trace gas budgets in the troposphere.  \n\nIce format
 ion measurement techniques and aerosol generation methods were developed  
 validated and implemented in order to address the above question. A number
  of tropospherically relevant particulates with naturally-varying and labo
 ratory-modified surface chemistry/structure were investigated for their ic
 e formation efficiency based on highest T and lowest RH required for ice f
 ormation.
LOCATION:CM 1 1 https://plan.epfl.ch/?room==CM%201%201
STATUS:CONFIRMED
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