Andreas Stohl

1

Arctic smoke

• Andreas Stohl
• and many others from NILU and elsewhere
• Norwegian Institute for Air Research (NILU)

2

What makes the Arctic so special in winter?
Arctic Haze first observed in the 1950s by
pilots Few pollution sources within the Arctic
itself, Arctic remote from major pollution
sources Long-range transport, mostly from
Eurasia Removal processes very slow or absent
(wet / dry deposition, photochemical
processing)
Shaw (1995) BAMS 76, 2403-2413
3

The polar dome
Zonal mean potential temperature, DJF
pressure
Polar dome
4

Average vertical profiles of potential
temperatures
Cracked ice
Strunin et al., Atmos. Res. 44, 37-51, 1997
Turbulence
Open water
Pack ice
Potential temperature (C)
5

Potential temperature, DJF
AMAP Assessment Report 1998
6

Position of the Arctic front in winter and in
summer
AMAP Assessment Report 1998
7

Surface sensible heat flux, DJF
8

Surface sensible heat flux, JJA
9

Seasonal variation of cloud cover and
precipitation
AMAP Assessment Report 1998
10

The time in darkness
Stohl (2006) J. Geophys. Res. 111, D11306,
doi10.1029/2005JD006888.

• December,
• the darkest month
• lowest 100 m
• of the atmosphere

11

The Arctic age of air
Time spent continuously north of 70N - Lowest
100 m of the troposphere
July January
Note the different scales!!!
12

The Arctic age of air
Average age of air north of 80N
13
Aerosols in the Arctic

• Aerosol light scattering at Barrow, Alaska (NOAA
  ESRL)

• Maximum in winter/spring so-called Arctic
  Haze
• Concentrations in summer much lower but not
  much research yet.

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Aerosols in the Arctic

• BUT Light absorbing aerosols (soot) have a
  high radiative forcing exactly in the Arctic
  summer

• Shortwave radiation is plenty.
• High albedo of snow and ice.
• High albedo of stratus cloud decks.
• Deposition of soot on snow and ice surfaces.

15

Winter-time transport to the Arctic troposphere
Continental BC contributions in dependence of time
Stohl (2006) J. Geophys. Res. 111, D11306,
doi10.1029/2005JD006888.
Lower troposphere
Total column
16

New issues Boreal forest fires
MODIS Terra image of Alaskan fire plume over the
Canadian Arctic in July 2004
Pyro-Cumulonimbus
82N
17

Summer-time transport to the Arctic troposphere
Continental BC contributions in dependence of time
Stohl (2006) J. Geophys. Res. 111, D11306,
doi10.1029/2005JD006888.
Lower troposphere
Total column
18
Forest fires in summer 2004
Stohl et al. (2006) JGR, in press

• 2004 was the most severe burning season in Alaska
• Strong fires also in western Canada
• gt 5 Million hectare burned in total

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FLEXPART Tracer SimulationTotal CO column
90N
Alert
80N
Barrow
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Comparison Model / Satellite image

• 5. Juli 2004
• FLEXPART Total Column MODIS satellite
  image

Alert
Barrow
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Barrow, Alaska

• Aerosol Optical Depth (AOD) measurements
  (symbols) and FLEXPART CO column (line)

normal value

• Soot measurements (black line) and FLEXPART CO
  tracer at the surface (colors give the age
  since emission)

Source analysis
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Barrow, Alaska

• Source analysis
• using a FLEXPART backward calculation

Emission sensitivity
Barrow
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Summit, Greenland

• Aerosol Optical Depth (AOD) measurements
  (symbols) and FLEXPART CO column (line)

normal value

• Soot measurements (black line) and FLEXPART CO
  tracer at the surface (colors give the age
  since emission)

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Zeppelin, Spitsbergen

• CO and soot measurements from May til September

? CO ? Anomaly
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Zeppelin, Spitsbergen

• Aerosol Optical Depth (AOD)-measurements
  (symbols) and FLEXPART CO column (line)

normal value
? CO anomaly ?

• Soot measurements (black line) and FLEXPART CO
  tracer at the surface (colors give the age
  since emission)

? fog, rain ?
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Effects on the albedo of snow

• Albedo at Summit, Greenland

Russ
27
Agricultural burning in Eastern Europe in
April/May 2006
Stohl et al. (2006) ACPD, in review
28
Record warmth in the European Arctic
Stohl et al. (2006) ACPD, in review
Temperature at Ny Ålesund, Spitsbergen in April
and May 2006 Warmth dismantles the polar dome
and creates effective pathway into the Arctic!
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Transport of fire emissions into the European
Arctic
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Extreme pollution
Picture courtesy Ann-Christine Engvall
31
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
formation was highly efficient!
32
Extreme pollution
At Iceland, a new ozone record was set, 15 ppb
higher than any previously measured value
33
Polluted snow at Holtedahlfonna observed by John
Burkhart
Snowmobile track ?
Polluted snow
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POLARCATPolar Study using Aircraft, Remote
Sensing, Surface Measurements and Models,
ofClimate, Chemistry, Aerosols, and Transport

• http//zardoz.nilu.no/andreas/POLARCAT/
• Contact me AST_at_NILU.NO