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NOx emissions estimates based on satellite observationsJieying Ding; Ronald van der A; Bas Mijling; PieternelLevelt
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Introduction
Input for air quality simulations and forecasts
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Emission inventory
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Emission estimates
´ Bottom-upapproach
Ø Statisticscombininglocalinformation:
• Emissionactivities
• Emissionfactors
• Sourcetypes
´ Satellite-basedapproach
Ø Inversionmethodscombiningsatelliteobservationsandchemicaltransportmodel:
• 4DVARtechniques(Stavrakou etal.,2008)
• Kalman filter(Mijling etal.,2012)
• EnsembleKalman filter(Miyazakietal.,2012)
• ……
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Whatdoweactuallyseefromspace?
NOxEmissions?
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Key part: the sensitivity of the observed NO2 column concentration on the NOx emissions in the CTM
EmissionsA priori
emissions
Inversion based on
Kalman filter
Next time step
Satellite Observations
CTM
DECSO: Daily emission estimates constrained by satellite observations
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A Case study
´The Nanjing Youth Olympic Games
Population: 8.2 million Date: 16 to 24 August, 2014Regulations taken by local government
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Can we see the effect on emissions via satellite observations?
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A decrease of 32% in August. But this could be caused by the rainy weather.
A reduction about 10%
A reduction about 25%
*Ding,J.,vanderA,R.J.,Mijling,B.,Levelt,P.F.,andHao,N.:NOx emissionestimatesduringthe2014YouthOlympicGamesinNanjing,Atmos.Chem.Phys.,15,9399-9412,doi:10.5194/acp-15-9399-2015,2015.
Satellite observations vs. satellite-derived emissions
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Ship emissions near the Chinese coast areas; 55 Gg N per year
Comparable to ship locations:
Shipping emissions derived from space
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Intercomparison: temporal evaluation
Standard deviation: 1 Tg N yr-1 in 2008, about 20% of the average
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Intercomparison: spatial distribution
• High correlation of emission distribution on a provincial level : R> 0.8
• Good agreement of emissions along latitude
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Bottom-up approach Satellite-derived approach
o Detailed information about emission source types
o Uncertainties from the statisticso Infrequent update
o Fast update: daily and globalo Difficulty: distinguish emissions
from different source categories
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Recommendations
Ø Satellite-based approach is able to detect NOx emission change in a
short time period.
Ø Satellite-derived emissions are in good agreement with bottom-up
emissions.
Ø The information from satellite-based approach and bottom-up
approach can be combined.
Conclusions