Model Simulation of tropospheric BrO

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Model Simulation of tropospheric BrO
Xin Yang, J. Pyle and R. Cox Center for
Atmospheric Science University of Cambridge 7-9
Oct. 2007. Frascati, Italy
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Basic model information

• Model a 3D global chemical transport model,
  p-TOMCAT, with detailed bromine chemistry Yang
  et al., JGR, 2005.
• Br sources 6 bromocarbons and sea salt from both
  open ocean and polar sea ice surface due to
  wind-driven production. A new size-dependent Br
  depletion factor for sea salt aerosols
• Br-Chemistry adding 3 heterogeneous
  reactivations on aerosols, such as
  HBrHOBrBr2H2O
• Forcing field ECWMF reanalysis data (every
  6hrs)
• Resolutions T42 (2.8x2.8 degrees) x 31 vertical
  layers
• Simulation period 1998
• Output frequency 2hrs (to match GOME SZA for
  BrO)

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Bromine chemical scheme in p-TOMCAT model
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Comparison with GOME in March
The upper figure is the simulated monthly mean
(March) daytime (9am-3pm) tropospheric column
BrO(1013 molecules/cm2 ). The bottom figure is
GOME BrO tropstrat Basically, the model
captured the main feature of the GOME BrO in
arctic with large level along Arctic coasts and
over northern American (Good). An exception is
over Greenland sea where model see a big BrO but
GOME did not (Good or bad?) Satellite is less
sensitive over open water? In SH, its autumn
tropospheric BrO is about 2 1013 molecules/cm2,
about 2 times of NH autumn level (Good) In the
tropics, the lowest tropospheric BrO is 0.5
1013 molecules/cm2
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Comparison with GOME in Sep.

• Basically, the model captured the main structure
  of the ring-like high BrO around Antarctic during
  SH spring. Good
• The simulated BrO in SH spring is higher than
  that in the NH spring. (Bad ?)
• If model problem
• 1) overestimated Br depletion factor for seasalts
  
• 2) not including humidity effect on sea salt
  production
• If true underestimated by satellite due to less
  ice cover in Southern Ocean
• In NH, its autumn tropospheric BrO is about 1
  1013 molecules/cm2, which is only half of SH
  autumn level (Good).

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Over Barrow
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In the NH
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1998
Comparison between ground-based UV-vis and
modeled tropospheric and stratospheric BrO
columns. By Hendrick et al., ACP-2007-0224.
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In the SH
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Satellite can not see BrO explosions happened in
early spring in the SH (?!) This is consistent
with ship measurement by Wagner et al., ACP, 2007
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Zonal mean BrO (pptv)
O3 loss ()
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Possible further collaboration

• We hope to work together with scientist in this
  fields to validate our model through more
  comparisons with derived-BrO data from both
  satellite and ground based measurements. These
  comparisons can be in short time scale, such as
  daily variation, or in long time scale, such as
  seasonal or year-to-year variation, even in long
  term trend.
• We hope TEMIS to supply more satellite column BrO
  data on global scale for further comparison,
  especially over the sites where high BrO events
  frequently happen, such as coastal regions of
  Arctic, Hudson bay, in SH over Weddle Sea and
  Rose Sea.
• We also hope observers to pay some attentions on
  the potential high BrO plumes over regions
  where are open water in local spring. For
  example, over Greenland Sea and off the main ice
  sheet in the Southern Ocean.

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Thanks

• Invitation by TEMIS/SEA
• EU project THALOZ
• NCAS/NERC, UK

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Ozone loss
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Vertical diffusion and emission effects on O3
loss