Andreas Stohl Norwegian Institute for Air Research (NILU)
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Andreas Stohl
Norwegian Institute for Air Research (NILU)
and
E. Andrews, T. Berg, J. F. Burkhart, A. M. Fjæraa, C. Forster, A. Herber, S.
Hoch, Ø. Hov, D. Kowal, C. Lunder, T. Mefford, W. W. McMillan, J. A.
Ogren, S. Oltmans, S. Sharma, M. Shiobara, D. Simpson, S. Solberg,
N. Spichtinger, K. Stebel, R. Stone, J. Ström, R. Treffeisen, K.
Tørseth, K. Virkkunen, C. Wehrli, and K. E. Yttri
Some current science problems
regarding Arctic air pollution
Aerosol radiative forcing
Aerosol direct radiative forcing is different from any other place
• large solar zenith angles
• pronounced haze layers
• high surface albedo (snow, ice, stratus cloud decks)
lead to multiple scattering/reflection between haze layers and
the surface and enhance the relevance of light absorption
Aerosol indirect radiative forcing could be positive in the Arctic
• no solar radiation in winter
• Arctic clouds so thin that they are greybodies in the
longwave, making them susceptible to aerosol effects in
the longwave (thermal radiation)
Thus, positive forcing, opposed to the shortwave effects
Some current science problems regarding Arctic air pollution Albedo effects Black carbon important light absorber in the atmosphere, but also when deposited on the ground, as it reduces the albedo of snow/ice surfaces. The efficacy of this effect is about twice as large as that of CO2, thus leading to pronounced effects on the surface temperatures and sea ice melting.
Some current science problems regarding Arctic air pollution Uncertain sources of Arctic air pollution One study (Koch and Hansen, 2005) suggests South Asia as the main source of Black Carbon, another (Stohl, 2006) rejects this hypothesis – quite heavily debated just recently in a workshop on Arctic climate forcing. Stohl (2006) suggests a ”new” source of Black Carbon to be dominant in summer: biomass burning (esp. boreal forest fires) Pyro-convection can inject aerosols into the high-latitude stratosphere
Some current science problems regarding Arctic air pollution Ozone depletion events In springtime, ozone can disappear almost completely at surface stations ”Bromine clouds” responsible, but unclear where the bromine originates
Satellites and models have
problems in the Arctic
Satellites
• No data from geostationary satellites
• No light in winter – no observations in the shortwave
• Large solar zenith angles in summer – still problems
• High albedo of snow and ice – aerosol optical depth
unreliable
Models
• Highly stable atmosphere – thin layers that cannot be
resolved
• Many global models use a latitude/longitude grid – singularity
at the pole, which may lead to incorrect transport in large
parts of the Arctic
IASOA observatories
Stohl (2006): J. Geophys. Res. 111, D11306, doi:10.1029/2005JD006888.
December,
the darkest month
- lowest 100 m
Inte
rcon of the atmosphere
tine
ntal
tran
s portTime spent continuously north of 70°N - Lowest 100 m of the
troposphere
July January
Note the different scales!!!Stohl (2006): Characteristics of atmospheric transport into the Arctic troposphere.
J. Geophys. Res. 111, D11306, doi:10.1029/2005JD006888.
Average age of air north of 80°NContinental BC contributions in dependence of time from a
FLEXPART tracer model simulation
– no chemistry, no removal, only transport using BC
emission inventory from T. Bond
Lower troposphere Total columnContinental BC contributions in dependence of time
BC inventories from T. Bond and D. Lavoue (boreal fires)
Lower troposphere Total columnPan-Arctic enhancements of light absorbing aerosol concentrations
due to North American boreal forest fires during summer 2004
Stohl et al. (2006): JGR, 111, D22214,
doi:10.1029/2006JD007216. • 2004 was the most severe burning
season in Alaska
Pyro-Cb • Strong fires also in western
Damoah et al. (2006):
Canada
Atmos. Chem. Phys. 6, 173-185.
• > 5 million hectare burnedFLEXPART Tracer Simulation:
Total CO column
90°N
Alert
80°N
BarrowComparison model / satellite image
5. July 2004
FLEXPART Total Column MODIS satellite image
Alert
BarrowBarrow, Alaska
• Aerosol Optical
Depth (AOD)
measurements
(symbols) and
FLEXPART CO column
(line)
”normal” value
• EBC measurements Source analysis
(black line) and
FLEXPART CO tracer
at the surface
(colors give the
”age” since
emission)Barrow, Alaska
Source analysis
using a FLEXPART backward calculation
Emission sensitivity
BarrowSummit, Greenland
• Aerosol Optical
Depth (AOD)
measurements
(symbols) and
FLEXPART ”normal” value
CO column (line)
• EBC measurements
(black line) and
FLEXPART CO tracer
at the surface
(colors give the
”age” since
emission)Zeppelin,
Spitsbergen
• CO and EBC
measurements from May
til September
◀ CO ▶
AnomalyZeppelin,
Spitsbergen
• Aerosol Optical
Depth (AOD)-
measurements
”normal”
(symbols) and
value
FLEXPART CO column
(line)
◀ CO anomaly ▶
◀ fog, rain ▶
• EBC measurements
(black line) and
FLEXPART CO tracer
at the surface
(colors give the
”age” since
emission)Effects on the albedo of snow
Albedo at Summit, Greenland
Snow drift
Fresh snowArctic smoke – record high air pollution levels in
the European Arctic due to agricultural fires in
Eastern Europe
Stohl et al. (2006): Atmos. Chem. Phys. Discuss. 6, 9655–9722.
Fire detections in April/May 2006Record warmth in the European
Arctic
Temperature at
Ny Ålesund,
Spitsbergen in
April and May
2006
Warmth
”dismantles” the
polar dome and
creates effective
pathway into the
Arctic!Transport of fire emissions into
the European ArcticExtreme pollution
Picture courtesy: Ann-Christine EngvallExtreme pollution At Zeppelin, new records were set for practically all measured compounds Ozone, aerosol optical depth (both measured for about 15 years!) Carbon monoxide, particulate matter, etc. Ozone formation was highly efficient!
Extreme pollution At Iceland, a new ozone record was set, 15 ppb higher than any previously measured value
Polluted snow at Holtedahlfonna
observed by John Burkhart
Snowmobile track
←
Polluted
snow
Ion chromatographic analysis of
snow samples confirms BB source.POLARCAT
Polar Study using Aircraft, Remote Sensing, Surface
Measurements and Models, of
Climate, Chemistry, Aerosols, and Transport
http://www.nilu.no/polarcat
Contact me: AST@NILU.NOHow? When? Where?
Major Campaigns
1. March/April 2007: 2 aircraft based in Longyearbyen, Svalbard
2. February-May 2008: Approximately 5 aircraft, based at various
locations throughout the Arctic, plus a ship cruise from
North America to the Norwegian Sea
3. June-August 2008: Up to 10 aircraft based in Canada, Russia,
Europe, Greenland, etc.; measurements with a railway carriage
along the Transsiberian railroad
Surface stations
Zeppelin, Barrow, Summit, etc.: long-term monitoring, plus intensive
campaigns Some of the
POLARCAT
Satellite data
Retrievals will be made inplatforms
near-real....
time for flight planning, and
for post-mission analyses; algorithm validation and improvement
Models
A variety of chemistry-climate, chemistry-transport, and pure
transport models will be usedYou can also read
