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- Title
The Role of Emission Sources and Atmospheric Sink in the Seasonal Cycle of CH 4 and δ 13 -CH 4 : Analysis Based on the Atmospheric Chemistry Transport Model TM5.
- Authors
Kangasaho, Vilma; Tsuruta, Aki; Backman, Leif; Mäkinen, Pyry; Houweling, Sander; Segers, Arjo; Krol, Maarten; Dlugokencky, Edward J.; Michel, Sylvia; White, James W. C.; Aalto, Tuula
- Abstract
This study investigates the contribution of different CH4 sources to the seasonal cycle of δ 13 C during 2000–2012 by using the TM5 atmospheric transport model, including spatially varying information on isotopic signatures. The TM5 model is able to produce the background seasonality of δ 13 C, but the discrepancies compared to the observations arise from incomplete representation of the emissions and their source-specific signatures. Seasonal cycles of δ 13 C are found to be an inverse of CH4 cycles in general, but the anti-correlations between CH4 and δ 13 C are imperfect and experience a large variation ( p = −0.35 to −0.91) north of 30° S. We found that wetland emissions are an important driver in the δ 13 C seasonal cycle in the Northern Hemisphere and Tropics, and in the Southern Hemisphere Tropics, emissions from fires contribute to the enrichment of δ 13 C in July–October. The comparisons to the observations from 18 stations globally showed that the seasonal cycle of EFMM emissions in the EDGAR v5.0 inventory is more realistic than in v4.3.2. At northern stations (north of 55° N), modeled δ 13 C amplitudes are generally smaller by 12–68%, mainly because the model could not reproduce the strong depletion in autumn. This indicates that the CH4 emission magnitude and seasonal cycle of wetlands may need to be revised. In addition, results from stations in northern latitudes (19–40° N) indicate that the proportion of biogenic to fossil-based emissions may need to be revised, such that a larger portion of fossil-based emissions is needed during summer.
- Subjects
ATMOSPHERIC chemistry; ATMOSPHERIC transport; CHEMICAL models; SEASONS; ATMOSPHERIC models; ATMOSPHERIC methane; WETLANDS
- Publication
Atmosphere, 2022, Vol 13, Issue 6, p888
- ISSN
2073-4433
- Publication type
Article
- DOI
10.3390/atmos13060888