Download from WMO (2007), based on Sinnhuber and Folkins, ACP (2006)

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Transcript
The impact of short-lived source gases
on the ozone layer under
the influence of a changing climate
A proposed contribution to G-SPARC
Björn-Martin Sinnhuber
Institute of Environmental Physics
University of Bremen
December 2006
Very Short-Lived Source gases: The paradigm
from WMO (2003)
2
Open issues
• What is the (current) contribution of very short-lived source
(VSLS) gases to stratospheric ozone depletion?
• How are VSLS transported through the tropical tropopause
layer (TTL) into the stratosphere?
• Rate of convective transport into the upper troposphere / lower
stratosphere
• Chemical degradation in the TTL
• Wet removal of degradation products from the TTL
• How will the contribution of VSLS change in a changing
climate?
• How will the (oceanic / biogenic) sources change?
• How will the transport processes (incl. wet removal) change?
3
Future Considerations for Halogenated VSLS (WMO, 2007)
• Possible future changes in anthropogenic VSLS. If anthropogenic
emissions increased, or if presently unused halogenated VSL SGs
were to come into widespread commercial use, then halogenated
VSLS would become of increased importance in affecting the future
behavior of stratospheric ozone.
• Delivery of VSLS to the stratosphere may change in the future in
response to circulation changes.
The impact of natural
halogenated VSLS might also be influenced by changes in the
atmospheric circulation, which could, for example, increase the rate of
delivery of VSL SGs and PGs into the stratosphere.
• Natural VSLS emissions may respond to future changes in
climate processes. Natural sources could respond to changes in, for
example, CO2, land use, wind speed, and temperature.
Our knowledge about these potential effects, and many other
relevant feedbacks, is very limited at present.
4
Context
How will the emissions, transport, and effects of VSLS change in
a changing cimate ?
 addresses New SPARC Initiative 1 - Chemistry Climate
Interactions
 is of direct relevance for the (next, 2010) WMO/UNEP Scientific
Assessment of Ozone Depletion
 expands on previous work of our group
5
Previous work / related activities
• Investigation of SCIAMACHY BrO observations
(Sinnhuber et al., GRL, 2005; Sheode et al., ACP(D), 2006;
Alexei Rozanov: „BOOST“ BrO intercomparison / validation project)
• Modelling studies on the impact of bromine from VSLS on past
stratospheric ozone trends
(Sinnhuber et al., ACP(D), 2006)
• Idealized model studies on transport of VSLS through the TTL
(Sinnhuber and Folkins, ACP, 2006)
• Validation of convective transport in global models
(SCOUT-O3 WP 6.2; Folkins et al., JGR, 2006)
• Investigation of oceanic phytoplankton from SCIAMACHY
observations
(Astrid Bracher: DFG project „PASAT“; HGF Nachwuchsgruppe)
6
DJF
MAM
JJA
SON
from Sheode et al., ACP(D), 2006
BrO „climatology“ from SCIAMACHY observations
7
SCIAMACHY BrO: Stratospheric bromine from VSLS
SCIAMACHY BrO observations
suggest present contribution of
~3ppt bromine from very shortlived source gases.
from WMO (2007), based on
Sinnhuber et al., GRL (2005)
8
Impact of short-lived bromine on ozone trends
Additional bromine
from very short-lived
source gases has
significant impact on
calculated ozone
trends (in particular
for periods with
enhanced aerosol
loading).
from Sinnhuber et al.,
ACPD (2006)
9
Transport processes: Convective transport into the TTL
How will this respond to climate change
(e.g. changes in tropical SST and
tropospheric temperature) ?
from Sinnhuber and
Folkins, ACP (2006)
10
Importance of wet removal in the TTL: Model calculations
from WMO (2007), based on
Sinnhuber and Folkins, ACP
11
(2006)
Convective transport of VSLS: Model vs aircraft observations
Observations of
VSLS very limited
at present.
from Sinnhuber and
Folkins, ACP (2006)
12
Validation of modelled tropical tracer transport
Comparison of idealized tracers as
part of European IP SCOUT-O3.
Large differences in
modelled short-lived
tracers between different
models.
13
Observation of oceanic source regions from SCIAMACHY
Oceanic bromoform emissions related to
phytoplankton (in particular diatoms, e.g.
see Quack et al., GRL, 2004).
A. Bracher, DFG
project „PASAT“
14
Suggested methodology
Analysis of SCIAMACHY BrO (plus NO2, O3, ...) observations for VSLS
(All going well there will be ~10 years of SCIAMACHY data by the end of the
project)
Process oriented model studies to investigate transport of VSLS through
the TTL
•How will the transport processes (incl. wet removal) change for changes
in tropical SST ?
•Are the relevant processes adequately represented in current CCMs ?
Investigate how oceanic VSLS emissions may change for changes in
tropical SST
(e.g., investigate changes in plankton distribution and calculated air-sea fluxes
as a result of ENSO)
Full model calculations on the effect of VSLS in a changing climate
15
Extra slides
16
Very Short-Lived Source gases: The paradigm
from WMO (2007)
(update from WMO, 2003)
17
Validation of modelled tropical tracer transport
Bromoform - 20 day
Methyl Iodine - 5 day
Comparison of idealized tracers in different CTMs and CCMs as part
of European IP SCOUT-O3.
18
Chlorophyl concentration from MERIS
19
Suggested methodology
• Investigation of stratospheric BrO (and NO2, O3, ...) from
SCIAMACHY observations
• All going well there will be ~10 years of SCIAMACHY
observations towards the end of the project
• Investigate transport processes of VSLS and their sensitivity
to climate change from a range of modelling tools
• How will the transport processes (incl. wet removal) change for
changes in tropical SST ?
• Are the relevant processes adequately represented in current
CCMs?
• Can we learn anything about changes in oceanic biogenic
production in a changing climate?
• Analysis of SCIAMACHY observations (plus other data)
20