Image D. Anderson, NASA, from Seinfeld et al., BAMS, in press, 2003
Intercontinental Transport of Pollutants Out & Into Asia (emphasis on particles)
Intercontinental Transport of Pollutants Out & Into Asia
• What do we know about the transport mechanisms?
• How good are the models?
• What are the sources of uncertainty?
• What do the observations tell us?
• What are some next steps?
The CFORS forecast (upper left) of the two dust systems are shown above. The dust plume (pink) represents the region with dust concentrations greater than 200 grams/m3. White indicates clouds. The SeaWifs satellite image (upper right) also clearly shows the accumulation of dust spiraling into the Low Pressure center. Also note the strong outflow of dust in the warm sector “ahead” of the front over the Japan Sea. The two systems are clearly seen in the satellite derived TOMS-AI (aerosol index) (lower right). The dust event is clearly seen in the China SEPA air pollution monitoring network. Lower left hand panel shows extremely large ground level concentrations (http://www.ess.uci.edu/~oliver/tracep/airqual/index.html). The sandstorm and sand-drifting weather, which swept across most parts of China caused severe visibility and air quality problems
http://news.xinhuanet.com/english/20010409/395181.htm
NASA-Seawifs
• Convection
• Warm conveyor belt lifting
• Post-frontal boundary layer transport
• Low level pre-frontal
• Advection in the westerlies
• Cold front subsidence
• Large-scale subsidence
• Mountain wave subsidence
• Boundary layer transport
Transport Mechanisms: As informed by field experiments & models (e.g., Trace-P, Ace Asia, ITCT-2k2/Peace,
ICARTT, ABC)
Liang et al., JGR, 2004
Convection 8% of time accounts for ~35% of outflow flux
Oshima et al.,JGR, 2004
Example: Results from Peace/ITCT2K2
One Model’s View: One Spring
Dust
Sulfate
BC
Transport to Asia
viz. Newell and Evans [2000]
100°E
Wild, et al., 2004
How Good Are the Models?
Model inter-comparison studies focused on Asia: e.g., MICS-Asia, DMIP, Trace-P/Ace-Asia
Comparisons of predictions with observations
Sulfate concentration in March 2001 (g m-3)
contents
Model-1 Model-3 Model-4
Model-5 Model-6 Model-7 Model-8
Model-2
MICS Phase II Results: Concentrations agree better than deposition fluxes
http://www.adorc.gr.jp/adorc/mics.html
DMIPS: Dust inter-comparison study
Spread in mean vertical profiles
Uno et al., 2005
Receptor 7 - Oki (Japan)
0%
20%
40%
60%
80%
100%
1 2 3 4 5 6 7 8
Model Intercomparison Study (MICS) Asia:
Source/Receptor Predictions
http://www.adorc.gr.jp/adorc/mics.html
Receptor 17 - Taichung (Taiwan)
0%
20%
40%
60%
80%
100%
1 2 3 4 5 6 7 8
What are the Major Sources of Uncertainty in the Calculation of Aerosol Export?
0%
100%
200%
300%
400%
500%
600%
700%
800%
900%
China Japan Other EastAsia
SoutheastAsia
India OtherSouth Asia
Ships All Asia
(95%
Con
fiden
ce In
terva
l,
? )SO2
NOx
CO2
CO
CH4
VOC
BC
OC
NH3
Streets et al., JGR, 2003
Emissions
Predictions of wet deposition are markedly
different
Impact of Wet Removal on Predicted BC
Progress limited by lack of understanding and observations
Removal Processes Remain Poorly Characterized in Models
Emissions Wet
removal Chemical
Formation Vertical
Transport Model
Resolution Total
nss SO4 0.3 0.3 0.3 0.5 0.1 0.7
BC 3 1 -- 0.5 0.1 3.2
OC 3 1 3 0.5 0.1 4.3 Dust 5 1 -- 0.5 1 5.2
Sea Salt 5 0.3 -- 0.5 1 5.13
Summary of Major Sources of Uncertainty in the Calculations
Summary of estimated relative uncertainties* for integrated aerosol quantities (column amounts, fluxes)
*(uncertainty divided by mean value).
Note: for analysis of specific points some of these terms are larger…
How do the models perform with respect to observations?
BC
Sulfate Obs
M
Comparison of Predictions vs Obs for INDOEX and Ace-Asia (Ron Brown ship data)
Sub-micron Super-micron Total
Mass
Composition
Comparison of Observed and Predicted Chemical composition
(sub-micron mode)
0.0001
0.001
0.01
0.1
1
10
100
Export of Particles: One Model’s View -- One Spring
Models predict a larger fraction of BC & OC (wrt sulfate) is
transported out of Asia
What do the observations tell us?
Model-based Observation-based
~40% exported
Koike et al., JGR, 2003
Both approaches have large uncertainties !!
40%
Ace Asia Aerosol Column Means: Summary of Uncertainty, Model to Model Variability, and
Predictability (NOAA CCSP, ABC)
2 Models: MOZART
STEM
Final thoughts
Analysis is highly uncertain due to understanding, current state of models, inputs and available observations.
Presently observations are used to compare with predictions --- good for process development, confidence building.
Observations by themselves can not provide the answer -- models necessary …. but also can’t do it alone.
Improved understanding needed to reduce uncertainty: Processes (deposition) Role of clouds (transport & removal) Emissions
Expanded Monitoring Activities Will Provide Valuable new InformationExpanded Monitoring Activities Will Provide Valuable new Information EANET EANET ABCABC
Final thoughts (cont)
Enhanced measurements (systems and experimental designs) needed to constrain the problem
Final thoughts (cont) Integration of measurements and models needed…ensemble
and data assimilation (get uncertainies, inversion for emissions and removal parameters, etc.)
Amir et al., JGR 2005
McKeen et al., in
prep.