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Transcript of 2014_wien_egu

Regional XCO2 enhancement
Trends of anthropogenic CO2 and NO2 emissions derived from the satellite instrument SCIAMACHY
M. Reuter¹, M. Buchwitz¹, A. Hilboll¹,
A. Richter¹, O. Schneising¹, M. Hilker¹,
J. Heymann¹, H. Bovensmann¹, J.P. Burrows¹

¹University of Bremen, Institute of Environmental Physics, Bremen, Germany

Isolating the anthropogenic XCO2 signal
Conversion factor
Weekend effect
Overall, the conversion factor increases with time
The increase is driven by CO2 because NO2 is relatively constant
ΔXCO2 and ΔNO2 are (approximately) proportional to the corresponding emissions
I.e., relative trends of ΔXCO2 and ΔNO2 equal relative emission trends
No significant trend of the CO2-to-NOx emission ratio (F)
Negative CO2 trend balances similarly large NO2 trend
CO2 trend in agreement with the EDGAR emission inventory
We analyze simultaneous SCIAMACHY NO2 and XCO2 retrievals
We use
tracer for anthropogenic CO2
in order to isolate the anthropogenic signal
The observed
weekend effect of CO2
proves that we indeed analyze an anthropogenic signal
No significant trend of the CO2-to-NOx emission ratio in North America and Europe
CO2-to-NOx emission ratio
with 4.2%/a in
East Asia
Interpretation: Even though East Asian NOx emissions are still rising, we find a significant improvement of the specific emissions attributed to successful NOx emission regulation efforts
Future analyses will profit from instruments with higher spatial resolution (e.g., CarbonSat in combination with Sentinel 5)
CO2 and NO2 are co-emitted when combusting fossil fuels
Anthropogenic XCO2 signal hidden by (smooth and uncorrelated):
Biospheric signals
Year-to-year increase
Background concentration
Calculate regional anomalies
ΔXCO2 and ΔNO2
by subtracting the average of all other measurements within 250km
Negative and neutral regional anomalies are also possible
XCO2 enhancements are only expected in cases with positive NO2 anomalies
Reject cases with negative anomalies

reduces due to

reduces due to

mixing and decay
Their fraction changes downwind
Large ΔXCO2 values can be expected where ΔNO2 is large

We find a roughly
linear relationship
between ΔNO2 and ΔXCO2
can be interpreted as
conversion factor
The conversion factor can vary regionally due to NO2 chemistry, emission ratio, fossil fuel mix, ...
N.America+EU: 0.32ppm / 10^16molec. cm-2
East Asia: 0.36ppm / 10^16molec. cm-2
Average enhancements
are reasonable for SCIAMACHY pixel size
We use the conversion factor
to translate NO2 measurements into
expected XCO2 enhancement due to nearby anthropogenic point sources
): XCO2e = F * NO2
lower ΔXCO2
values (~35±25%)
at weekends
in North America and Europe but not in East Asia
The weekend effect of XCO2 is a tiny signal and have
detected before
Its detection underlines that the analyzed CO2 signals originate from anthropogenic activities
North America and Europe
East Asia
The CO2-to-NOx emission ratio (F) is increasing with 4.2%/a resulting from
increasing CO2 emissions (9.8%/a) dominating the
increasing NOx emissions (5.8%/a)
CO2 is a proxy for the amount of combusted fossil fuel
Less and less NOx is emitted per CO2
New installed technology (power plants, transportation, etc.) is cleaner in terms of NOx
Note: this removes all smooth large scale signals
Remote sensing anthropogenic CO2 emissions is challenging because regional enhancements of individual point sources are:
orders of magnitude smaller than the background concentration
superimposed by dominating biospheric signals and the year-to-year increase
Global anthropogenic CO2 emission inventories:
Mainly based on bottom-up estimates
Rely, e.g., on reported fossil fuel consumptions and fuel types
Moderate to high confidence in industrialized regions of Europe and North America
Low confidence in other regions of the world (e.g., China)
The uncertainties of emission inventories propagate into:
CO2-to-NOx emission ratios (important for pollution monitoring)
Biospheric carbon fluxes derived with inverse models

NO2 and NO (NOx) are unwanted co-emitted by-products of fossil fuel combustion processes In the troposphere
In anthropogenic source regions of CO2, the largest part of tropospheric NO2 originates from the combustion of fossil fuels
It has a short lifetime (hours) and its vertical column densities can exceed background levels by orders of magnitude near sources
Therefore, NO2 is a suitable tracer for (recently emitted) anthropogenic CO2

Simultaneous XCO2 and NO2 satellite retrieval
Was operational roughly one decade (2002-2012)
Its wide spectral range (240nm-2400nm) allows simultaneous multi-species measurements
Within this study we use:
Column-average dry-air mole fractions of atmospheric CO2 (XCO2)
NO2 vertical column amounts

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