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- Title
Methane flux, vertical gradient and mixing ratio measurements in a tropical forest.
- Authors
Querino, C. A. S.; Smeets, C. J. P. P.; Vigano, I.; Holzinger, R.; Moura, V.; Gatti, L. V.; Martinewski, A.; Manzi, A. O.; de Araújo, A. C.; Röckmann, T.
- Abstract
Measurements of CH 4 mixing ratio, vertical gradients and turbulent fluxes were carried out in a tropical forest (Reserva Biologica Cuieiras), about 60 km north of Manaus, Brazil. The methane mixing ratio and flux measurements were performed at a height of 53m (canopy height 35m). In addition, vertical CH4 gradients were measured within the canopy using custom made air samplers at levels of 2, 16 and 36m above ground. The methane gradients within the canopy reveal that there is a continuous methane source at the surface. No clear evidence for aerobic methane emission from the canopy was found. The methane fluxes above the canopy are small but consistently upwards with a maximum early in the morning. The measured fluxes are in agreement with the observed CH4 gradient in the canopy. In the morning hours, a strong canopy venting peak is observed for both CH4 and CO2, but for CO2 this peak is then superimposed by photosynthetic uptake, whereas the peak lasts longer for CH4. Monthly averaged diurnal cycles of the CH4 mixing ratio show a decrease during daytime and increase during nighttime. The magnitude of the difference in CH4 mixing ratio between day and night gradually increases throughout the wet season. The fluxes required to explain the nighttime increase are in agreement with the nighttime fluxes measured above the canopy, which implies that the CH4 increase in the nighttime boundary layer originates from local sources.
- Subjects
ATMOSPHERIC methane; ATMOSPHERIC turbulence; EMISSIONS (Air pollution); PHOTOSYNTHESIS; ATMOSPHERIC boundary layer; DIURNAL variations in meteorology; SURFACE chemistry
- Publication
Atmospheric Chemistry & Physics, 2011, Vol 11, Issue 15, p7943
- ISSN
1680-7316
- Publication type
Article
- DOI
10.5194/acp-11-7943-2011