Dehydration and Condensation during STREAM 1998

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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

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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

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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

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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)

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Meteorological Situation
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In-situ Observations (2)
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H2O-O3 Correlation
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Composition of the particles?
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Microphysical Box Model

• Processes
• - Nucleation
• - Coagulation
• - Condensation
• STREAM 1998 Condensation of H2O on the liquid
  H2SO4/H2O aerosol particle
• Trajectories 10-days backward
  

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Trajectories
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Ice Saturation
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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

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Box Model Results
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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