Water Vapor modelling using SUNYA CCM3

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Water Vapor modelling using SUNYA CCM3

• Line Gulstad, Department of Geophysics,
  University of Oslo
• Supervisors Ivar S.A. Isaksen and Jostein K.
  Sundet

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• This work is a part of the CHEMCLIM project. The
  main goal is to study water vapor in the UTLS
  region and its interaction with other chemical
  compounds and climate.
• The work is done in collaboration with Prof.
  W.-C.Wang and his group at the State University
  of New York, (SUNY), Albany.
• We participate in the EU project SCENIC which is
  a collaboration between atmospheric scientists
  and the aviation industry. Our part is to
  consider various options for the change in water
  vapor in the UTLS region resulting from the
  proposed supersonic civil transport fleet.

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WATER VAPOR IN THE UPPER TROPOSPHERE AND
STRATOSPHERE

• Probably the most important greenhouse gas
• Involved in important climate feedback loops
• Nearly conserved trace species in the lower
  stratosphere and thus an important indicator for
  stratospheric transport
• Important component i stratospheric chemistry
• - methane oxidation
• - formation of stratospheric clouds
• - destruction of ozone
• Important for local diabatic heating

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OBSERVED INCREASE IN STRATOSPHERIC WATER VAPOR

• 10 datasets covering the years 1954 2000
• show 1 increase pr. year in stratospheric
• water vapor. Rosenlof et al.(2002)
• This increase yields an amount
• of 2ppmv which is an extreme
• increase when stratospheric
• water vapor to day varies
• between 3 and 6ppmv and looks
• something like this

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• Increased emissions of methane at the surface
  gives rise to an increase of water vapor in
• the stratosphere due to methane oxidation
• CH4OH ? CH3 H2O
• A warming troposphere gives more available water
  vapor
• Increased aircraft emissions
• Changes in circulation patterns
• Increased sea surface temperature
• Subvisible cirrus clouds in the tropopause region
• ..... and many other theories .....

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Model Description

• SUNYA CCM3 is a general circulation model based
  on NCAR/CCM3.
• The model is a global spectral (in horizontal
  direction) model with T42 spectral resolution
  (approximately 2.8ºx2.8º).There are 18 vertical
  levels in a generalized terrain-following hybrid
  vertical coordinate. Kiehl et. al. (1996, 1998).
• The 18 vertical levels correspond to about 2km or
  40-70mb vertical resolution near the tropopause.
• The overall dynamical timestep is of 20minutes
  for dynamics and physics. Radiation calculations
  are performed every hour. Hack et al. (1993)
• The model is in this case run for the years
  1979-1994 with observed sea surface temperatures.

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Comparison model and NCEP reanalysis Jan. 1992
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Comparison model and NCEP reanalysis July 1992
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Comparison HALOE and model Jan. mean
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Comparison HALOE and model July mean
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Ongoing and further work

• We are running the model with simple methane
  chemistry included.
• Aircraft emission scenarios for the years 2025
  and 2050 will be implemented in the model to
  estimate the future supersonic fleets impact on
  UTLS water vapor as a part of the EU project
  SCENIC
• Get a better understanding of the processes
  controlling the stratospheric water vapor
  increase and the impact this will have on
  chemistry and climate.
• Water vapor transport mechanisms across the
  tropopause.