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| Titel |
Exploring causes of interannual variability in the seasonal cycles of tropospheric nitrous oxide |
| VerfasserIn |
C. D. Nevison, E. Dlugokencky, G. Dutton, J. W. Elkins, P. Fraser, B. Hall, P. B. Krummel, R. L. Langenfelds, S. O'Doherty, R. G. Prinn, L. P. Steele, R. F. Weiss |
| 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 ; 11, no. 8 ; Nr. 11, no. 8 (2011-04-21), S.3713-3730 |
| Datensatznummer |
250009644
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| Publikation (Nr.) |
 copernicus.org/acp-11-3713-2011.pdf |
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| Zusammenfassung |
| Seasonal cycles in the mixing ratios of tropospheric nitrous oxide
(N2O) are derived by detrending long-term measurements made at sites
across four global surface monitoring networks. The detrended monthly data
display large interannual variability, which at some sites challenges the
concept of a "mean" seasonal cycle. In the Northern Hemisphere,
correlations between polar winter lower stratospheric temperature and
detrended N2O data, around the month of the seasonal minimum, provide
empirical evidence for a stratospheric influence, which varies in strength
from year to year and can explain much of the interannual variability in the
surface seasonal cycle. Even at sites where a strong, competing, regional
N2O source exists, such as from coastal upwelling at Trinidad Head,
California, the stratospheric influence must be understood to interpret the
biogeochemical signal in monthly mean data. In the Southern Hemisphere,
detrended surface N2O monthly means are correlated with polar spring
lower stratospheric temperature in months preceding the N2O minimum,
providing empirical evidence for a coherent stratospheric influence in that
hemisphere as well, in contrast to some recent atmospheric chemical
transport model (ACTM) results. Correlations between the phasing of the
surface N2O seasonal cycle in both hemispheres and both polar lower
stratospheric temperature and polar vortex break-up date provide additional
support for a stratospheric influence. The correlations discussed above are
generally more evident in high-frequency in situ data than in data from
weekly flask samples. Furthermore, the interannual variability in the
N2O seasonal cycle is not always correlated among in situ and flask
networks that share common sites, nor do the mean seasonal amplitudes always
agree. The importance of abiotic influences such as the stratospheric influx
and tropospheric transport on N2O seasonal cycles suggests that, at
sites remote from local sources, surface N2O mixing ratio data by
themselves are unlikely to provide information about seasonality in surface
sources, e.g., for atmospheric inversions, unless the ACTMs employed in the
inversions accurately account for these influences. An additional abioitc
influence is the seasonal ingassing and outgassing of cooling and warming
surface waters, which creates a thermal signal in tropospheric N2O that
is of particular importance in the extratropical Southern Hemisphere, where
it competes with the biological ocean source signal. |
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