Nitrous oxide emissions 1999 to 2009 from a global atmospheric inversion
N<sub>2</sub>O surface fluxes were estimated for 1999 to 2009 using a time-dependent Bayesian inversion technique. Observations were drawn from 5 different networks, incorporating 59 surface sites and a number of ship-based measurement series. To avoid biases in the inverted fluxes, the...
| Main Authors: | , , , , , , , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2014-02-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | http://www.atmos-chem-phys.net/14/1801/2014/acp-14-1801-2014.pdf |
| Summary: | N<sub>2</sub>O surface fluxes were estimated for 1999 to 2009 using a
time-dependent Bayesian inversion technique. Observations were drawn from 5
different networks, incorporating 59 surface sites and a number of ship-based
measurement series. To avoid biases in the inverted fluxes, the data were
adjusted to a common scale and scale offsets were included in the
optimization problem. The fluxes were calculated at the same resolution as
the transport model (3.75° longitude × 2.5° latitude)
and at monthly time resolution. Over the 11-year period, the global total
N<sub>2</sub>O source varied from 17.5 to 20.1 Tg a<sup>−1</sup> N. Tropical and
subtropical land regions were found to consistently have the highest N<sub>2</sub>O
emissions, in particular in South Asia (20 ± 3% of global total),
South America (13 ± 4%) and Africa (19 ± 3%), while
emissions from temperate regions were smaller: Europe (6 ± 1%) and
North America (7 ± 2%). A significant multi-annual trend in
N<sub>2</sub>O emissions (0.045 Tg a<sup>−2</sup> N) from South Asia was found and
confirms inventory estimates of this trend. Considerable interannual
variability in the global N<sub>2</sub>O source was observed (0.8 Tg a<sup>−1</sup> N,
1 standard deviation, SD) and was largely driven by variability in tropical
and subtropical soil fluxes, in particular in South America
(0.3 Tg a<sup>−1</sup> N, 1 SD) and Africa (0.3 Tg a<sup>−1</sup> N, 1 SD).
Notable variability was also found for N<sub>2</sub>O fluxes in the tropical and
southern oceans (0.15 and 0.2 Tg a<sup>−1</sup> N, 1 SD, respectively).
Interannual variability in the N<sub>2</sub>O source shows some correlation with
the El Niño–Southern Oscillation (ENSO), where El Niño conditions
are associated with lower N<sub>2</sub>O fluxes from soils and from the ocean and
vice versa for La Niña conditions. |
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| ISSN: | 1680-7316 1680-7324 |