Andreas StohlNorwegian 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
unreliableModels
• 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
December,the darkest month
- lowest 100 mof the atmosphere
Stohl (2006): J. Geophys. Res. 111, D11306, doi:10.1029/2005JD006888.
Intercontinental transport
July January
Time spent continuously north of 70°N - Lowest 100 m of the troposphere
Note the different scales!!!
Average age of air north of 80°N
Stohl (2006): Characteristics of atmospheric transport into the Arctic troposphere. J. Geophys. Res. 111, D11306, doi:10.1029/2005JD006888.
Continental 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 column
Continental BC contributions in dependence of time
BC inventories from T. Bond and D. Lavoue (boreal fires)
Lower troposphere Total column
• 2004 was the most severe burning season in Alaska
• Strong fires also in western Canada
• > 5 million hectare burned
Pan-Arctic enhancements of light absorbing aerosol concentrations
due to North American boreal forest fires during summer 2004Stohl et al. (2006): JGR, 111, D22214, doi:10.1029/2006JD007216.
Pyro-Cb
Damoah et al. (2006):
Atmos. Chem. Phys. 6, 173-185.
FLEXPART Tracer Simulation:Total CO column
Barrow
Alert
80°N
90°N
Comparison model / satellite image
5. July 2004
FLEXPART Total Column MODIS satellite image
Barrow
Alert
Barrow, Alaska
• Aerosol Optical Depth (AOD) measurements(symbols) and FLEXPART CO column(line)
Source analysis
”normal” value
• EBC measurements(black line) and FLEXPART CO tracerat the surface(colors give the ”age” sinceemission)
Barrow, Alaska
Source analysis
using a FLEXPART backward calculation
Barrow
Emission sensitivity
Summit, Greenland
• Aerosol Optical Depth (AOD) measurements(symbols) and FLEXPART CO column (line)
• EBC measurements(black line) and FLEXPART CO tracerat the surface(colors give the ”age” sinceemission)
”normal” value
Zeppelin, Spitsbergen
• CO and EBC measurements from May til September
◀ CO ▶Anomaly
Zeppelin, Spitsbergen
• Aerosol Optical Depth (AOD)-measurements(symbols) and FLEXPART CO column(line)
◀ fog, rain ▶
◀ CO anomaly ▶
• EBC measurements(black line) and FLEXPART CO tracerat the surface(colors give the ”age” sinceemission)
”normal”
value
Effects on the albedo of snow
Albedo at Summit, Greenland
Fresh snowSnow drift
Arctic smoke – record high air pollution levels in the European Arctic due to agricultural fires in
Eastern EuropeStohl et al. (2006): Atmos. Chem. Phys. Discuss. 6, 9655–9722.
Fire detections in April/May 2006
Record warmth in the European Arctic
Temperature at Ny Ålesund, Spitsbergen in April and May 2006
Warmth ”dismantles” the polar dome and creates effectivepathway into the Arctic!
Transport of fire emissions into the European Arctic
Extreme pollution
Picture courtesy: Ann-Christine Engvall
Extreme 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 formationwas highly efficient!
Extreme pollution
At Iceland, a new ozone record was set, 15 ppb higher thanany previously measured value
Polluted snow at Holtedahlfonnaobserved by John Burkhart
Snowmobile track←
Polluted
snow
Ion chromatographic analysis of snow samples confirms BB source.
POLARCATPolar Study using Aircraft, Remote Sensing, Surface
Measurements and Models, ofClimate, Chemistry, Aerosols, and Transport
http://www.nilu.no/polarcat
Contact me: [email protected]
How? When? Where?Major Campaigns
1. March/April 2007: 2 aircraft based in Longyearbyen, Svalbard2. 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 carriagealong the Transsiberian railroad
Surface stationsZeppelin, Barrow, Summit, etc.: long-term monitoring, plus intensive campaigns
Satellite dataRetrievals will be made in near-real time for flight planning, and for post-mission analyses; algorithm validation and improvement
ModelsA variety of chemistry-climate, chemistry-transport, and pure transport models will be used
Some of the POLARCAT platforms ....