Local verses Long-range Transport

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Local verses Long-range Transport
ACTIVE Meeting 21/05/09
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Ozone Evolution
Biomass Burning
Pre-monsoon
Monsoon Break
Monsoon
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Ozone CO Evolution
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(No Transcript)
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Back Trajectories

• 10-day back trajectories performed using ECMWF
  operational data from the trajectory server at
  the BADC
• Clustered trajectories were performed to check
  for consistency initally, with only the central
  trajectory used thereafter
• Performed for every ozone sounding (30) at every
  10 hPa between 900 and 200 hPa, and every 5 hPa
  between 200 and 100 hPa

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Back Trajectories
e.g.
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Back Trajectories
Now focus on the TTL region (200-100 hPa) Many
of the trajectories reaching the TTL show uplift
from low-level We now look at the location these
trajectories experience rapid uplift, choosing an
arbitrary level of 500 hPa for where these
trajectories cross.
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Ozone Concentrations
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Number of trajectories each represents
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Number of days before passing 500 hPa surface
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Advected trajectories
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Back Trajectories

• Similar analysis performed for CO
• Average background (out-of-cloud) CO
  concentrations taken for each transect (not vast
  change in concentration along transect
  out-of-cloud), and trajectories performed from
  aircraft location every 30 s.
• Clustered trajectories not required as
  consistency could be checked against neighbouring
  trajectories

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CO Concentrations
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Conclusions

• Origin of back-trajectoies show a consistent and
  coherent pattern which accounts for the variation
  in both ozone (from sondes) and CO (from
  aircraft)
• In general elevated ozone and CO can be
  attributed to sources over Indonesia, with
  reduced concentrations observed from the remote
  maritime Pacific
• Further supported by those trajectories advected
  over the course of the ten-days, which follow a
  similar pattern
• Thus the TTL above Darwin is governed by the
  wider tropical warm pool region as opposed to
  transport from the local boundary layer

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Conclusions

• Occasionally very low ozone was observed above
  Darwin and tracked to the remote Pacific.
• Ozone is not destroyed photochemically in the
  very dry tropical UT, so good evidence for
  widespread vertical mixing elsewhere, and
  advected into Darwin

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Conclusions
OVERALL The composition of the TTL is
ultimately determined by vertical mixing in
certain hot spot regions of the tropics, with
advection from these regions dominating the
composition elsewhere