AGU 2006 Highlights

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AGU 2006 Highlights

• Le Kuai
• Dec. 19, 2006

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Effects of Planetary Wave-induced Ozone Heating
on Downward Control Implications of Climate
VariabilityTerry Nathan and Eugene Cordero
Planetary wave drag (PWD) (the residual
circulation)

• Planetary
• wave

Stratospheric ozone heating
affect
Induce
downward control
troposphere
Climate system
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Effect of solar cycle on the troposphere-stratosph
ere coupling in the Southern Hemisphere
winterYuhji Kuroda

• Both the observation and simulation analysis
  indicate that the strength of the
  troposphere-stratosphere coupling tends to be
  stronger with the strength of the ultra violet
  (UV) radiation.
• Analysis indicates the coupling of the
  stratospheric Southern Annular Mode (S-SAM) in
  late winter with the upward planetary waves,
  ozone, and temperature variability is more
  prominent in the high solar year.

Stronger troposphere- Stratosphere Coupling in HS
years
Stronger UV Higher ozone
Dynamical interaction
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Arctic Ozone Loss and ClimateMarkus Rex, Ross J.
Salawitch, Timothy Canty, Peter von der Gathen,
Sabine Kleppek

• Interannual variability of chemical ozone loss in
  the Arctic is mainly driven by the winter average
  of air cold enough to allow for the existance of
  Polar Stratospheric Clouds (Vpsc).
• Maximum values of Vpsc reached during the cold
  Arctic winters increased by more than a factor of
  three. This change in the Arctic stratosphere
  contributed to the large ozone losses observed
  since the mid-1990s in the Arctic.
• Dynamical feedback mechanism
• 1) Rising GHG concentrations increase the
  meridional temperature gradient. This leads to
  changes in wave propagation properties and
  further cooling of the Arctic stratosphere.
• 2) Overall increasing momentum fluxes may make
  this situation less frequent, but once it occurs,
  colder conditions can develop.

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QBO Effects in a Chemistry Climate Model of the
Entire Atmosphere Hauke Schmidt, Marco A.
Giorgetta, and Guy P. Brasseur

• This study focus on possible effects of the QBO
  on chemistry and dynamics above the stratosphere.
• The Hamburg Model of the Neutral and Ionized
  Atmosphere (HAMMONIA) is a chemistry climate
  model that extends from the surface to the
  thermosphere.

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• Fig. 3 shows the annual mean ozone response to
  solar cycle UV variations as simulated by
  HAMMONIA from the surface to the lower
  thermosphere. The increase of ozone in the
  stratosphere and around the mesopause is caused
  by increased photodissociation of O2, the
  decrease in the upper mesosphere is due to
  increased OH caused by Lyman-adissociation of
  water vapor. Mesospheric and stratospheric
  responses are in the range suggested by
  observations. However, the uncertainty of
  existing observational analyses is large.
• Fig. 4 shows the annual mean temperature response
  to the solar cycle as simulated by HAMMONIA.
  However, relatively stable features of different
  observations are the upper stratospheric
  temperature increase and a secondary local
  response maximum in the equatorial lower
  stratosphere. This latter maximum is simulated to
  be strongest in northern hemisphere winter.
  Kodera and Kuroda (JGR, 2002) suggest a mechanism
  starting with increased heating in the summer
  upper stratosphere that leads to a slowing of the
  Brewer-Dobson circulation via wave-mean flow
  interactions, and finally to this lower
  stratospheric temperature increase.

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Thanks!