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| Titel |
Trends and variations in CO, C2H6, and HCN in the Southern Hemisphere point to the declining anthropogenic emissions of CO and C2H6 |
| VerfasserIn |
G. Zeng, S. W. Wood, O. Morgenstern, N. B. Jones, J. Robinson, D. Smale |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 12, no. 16 ; Nr. 12, no. 16 (2012-08-17), S.7543-7555 |
| Datensatznummer |
250011402
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| Publikation (Nr.) |
 copernicus.org/acp-12-7543-2012.pdf |
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| Zusammenfassung |
| We analyse the carbon monoxide (CO), ethane (C2H6) and hydrogen cyanide
(HCN) partial columns (from the ground to 12 km) derived from measurements
by ground-based solar Fourier Transform Spectroscopy at Lauder, New Zealand
(45° S, 170° E), and at Arrival Heights, Antarctica
(78° S, 167° E), from 1997 to 2009. Significant negative
trends are calculated for all species at both locations, based on the
daily-mean observed time series, namely CO
(−0.94 ± 0.47% yr−1), C2H6
(−2.37 ± 1.18% yr−1) and HCN
(−0.93 ± 0.47% yr−1) at Lauder and CO
(−0.92 ± 0.46% yr−1), C2H6
(−2.82 ± 1.37% yr−1) and HCN
(−1.41 ± 0.71% yr−1) at Arrival Heights. The uncertainties
reflect the 95% confidence limits. However, the magnitudes of the trends
are influenced by the anomaly associated with the 1997–1998 El Niño
Southern Oscillation event at the beginning of the time series reported. We
calculate trends for each month from 1997 to 2009 and find negative trends
for all months. The largest monthly trends of CO and C2H6 at Lauder,
and to a lesser degree at Arrival Heights, occur during austral spring during
the Southern Hemisphere tropical and subtropical biomass burning period. For
HCN, the largest monthly trends occur in July and August at Lauder and around
November at Arrival Heights. The correlations between CO and C2H6 and
between CO and HCN at Lauder in September to November, when the biomass
burning maximizes, are significantly larger that those in other seasons. A
tropospheric chemistry-climate model is used to simulate CO, C2H6, and
HCN partial columns for the period of 1997–2009, using interannually varying
biomass burning emissions from GFED3 and annually periodic but seasonally
varying emissions from both biogenic and anthropogenic sources. The
model-simulated partial columns of these species compare well with the
measured partial columns and the model accurately reproduces seasonal cycles
of all three species at both locations. However, while the model
satisfactorily captures both the seasonality and trends in HCN, it is not
able to reproduce the negative trends in either C2H6 or CO. A further
simulation assuming a 35% decline of C2H6 and a 26% decline of CO
emissions from the industrial sources from 1997 to 2009 largely captures the
observed trends of C2H6 and CO partial columns at both locations. Here
we attribute trends in HCN exclusively to changes in biomass burning and
thereby isolate the influence of anthropogenic emissions as responsible for
the long-term decline in CO and C2H6. This analysis shows that biomass
burning emissions are the main factors in controlling the interannual and
seasonal variations of these species. We also demonstrate contributions of
biomass burning emission from different southern tropical and sub-tropical
regions to seasonal and interannual variations of CO at Lauder; it shows
that long-range transport of biomass burning emissions from southern Africa
and South America have consistently larger year-to-year contributions to the
background seasonality of CO at Lauder than those from other regions (e.g.
Australia and South-East Asia). However, large interannual anomalies are
triggered by variations in biomass burning emissions associated with
large-scale El Niño Southern Oscillation and prolonged biomass burning
events, e.g. the Australian bush fires. |
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