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Dehydration and Condensation during STREAM 1998

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2 Department of Meteorology, Stockholm University, Sweden. Motivation ... H2O: Lyman- -Hygrometer measuring total water and O3: Ozone Chemiluminescence Monitor ( t=1s) ... – PowerPoint PPT presentation

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Title: Dehydration and Condensation during STREAM 1998


1
Dehydration and Condensation during STREAM 1998
  • F. Khosrawi1,2, J. Beuermann1, R. Müller1, P.
    Konopka1,
  • C. Schiller1 and E. D. Nilsson2
  • 1 ICG-I, Forschungszentrum Jülich, Germany
  • 2 Department of Meteorology, Stockholm
    University, Sweden

2
Motivation
  • Dehydration generally defined as irreversible
    process
  • ? strong evidence for preceding formation
  • of ice particles
  • ? Cirrus clouds
  • Cirrus clouds important role in the earths
    radiation budget and climate

3
STREAM1998 Campaign
  • STREAM Stratosphere-TRoposphere Experiments by
    Aircraft Measurements
  • Performed in Timmins, Kanada (July 1998)
  • Case study for the 15 July 1998
  • - Dehydration due to condensation of H2O and
    freezing with subsequent sedimentation

4
In-situ Observations (1)
  • Measurements of several trace gases
  • (e.g. H2O, CO, CO2, CFCs, N2O, NO)
  • Flight was conducted in dry and almost cloud free
    air (outward leg 7.8 km, return leg 9.8 km)
  • H2O Lyman-?-Hygrometer measuring total water and
    O3 Ozone Chemiluminescence Monitor (?t1s)

5
Meteorological Situation
6
In-situ Observations (2)
7
H2O-O3 Correlation
8
Composition of the particles?
9
Microphysical Box Model
  • Processes
  • - Nucleation
  • - Coagulation
  • - Condensation
  • STREAM 1998 Condensation of H2O on the liquid
    H2SO4/H2O aerosol particle
  • Trajectories 10-days backward

10
Trajectories
11
Ice Saturation
12
Box Model Studies
  • Particles are liquid and can only freeze after
    growing up to 1 ?m
  • Particles can only sediment after growing up to
    10 ?m in radius

13
Box Model Results
14
Conclusions
  • Ice particles have been formed, sedimented out
    and depleted the gas phase during STREAM 1998 (15
    July)
  • Box model calculations show no significant growth
    of the H2SO4/H2O particles
  • H2SO4/H2O particles do freeze at T lt 213 K
  • ? The ice particles probably have another
    composition than H2SO4/H2O/HNO3
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