On the validity of flux-gradient relationships above very rough surfaces

Cellier, Pierre

doi:10.1007/bf00118340

Cited by 27 publications

(12 citation statements)

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“…Simpson 1993). This technique cannot be used within canopies (Baldocchi et al 1988) and precautions should also be taken for locating high enough the lowest level of vertical profile above rough surfaces such as forest stands (Businger 1986;Cellier 1986). It should be located above the canopy, at about 100 times the roughness length.…”

Section: Techniques For Measuring Methanementioning

confidence: 99%

Soils as sources and sinks for atmospheric methane

Topp¹,

Pattey²

1997

Can. J. Soil. Sci.

192

115

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1997. Soils as sources and sinks for atmospheric methane. Can. J. Soil Sci. 77: 167-178. Methane is considered to be a significant greenhouse gas. Methane is produced in soils as the end product of the anaerobic decomposition of organic matter. In the absence of oxygen, methane is very stable, but under aerobic conditions it is mineralized to carbon dioxide by methanotrophic bacteria. Soil methane emissions, primarily from natural wetlands, landfills and rice paddies, are estimated to represent about half of the annual global methane production. Oxidation of atmospheric methane by well-drained soils accounts for about 10% of the global methane sink. Whether a soil is a net source or sink for methane depends on the relative rates of methanogenic and methanotrophic activity. A number of factors including pH, Eh, temperature and moisture content influence methane transforming bacterial populations and soil fluxes. Several techniques are available for measuring methane fluxes. Flux estimation is complicated by spatial and temporal variability. Soil management can impact methane transformations. For example, landfilling of organic matter can result in significant methane emissions, whereas some cultural practices such as nitrogen fertilization inhibit methane oxidation by agricultural soils.Key words: Methane, methanogenesis, methane oxidation, soil, flux measurement Topp, E. et Pattey, E. 1997. Le sol considéré comme source d'émission de méthane dans l'atmosphère. Can. J. Soil Sci. 77: 167-178. Le méthane est considéré comme gaz à effet de serre important : c'est le produit terminal de la décomposition de la matière organique en conditions anaérobies. En l'absence d'oxygène, il est très stable, mais en aérobiose, il est minéralisé en gaz carbonique par les bactéries méthanotrophes. Les émissions de méthane provenant surtout des terres humides naturelles, des décharges et des rizières représenteraient environ la moitié de la production annuelle de méthane dans la planète. Par ailleurs l'oxydation de méthane de l'atmosphère par les sols bien drainés compteraient pour environ 10 % du méthane stocké. Que le sol soit une source ou un puits d'accumulation nette de méthane, dépend des taux relatifs des activités méthanogéniques et méthan-otrophiques. Un certain nombre de facteurs, notamment, pH, Eh, la température et le niveau hydrique du sol, influent sur les populations bactériennes qui transforment le méthane ainsi que sur le flux de méthane dans le sol. On dispose de plusieurs techniques pour mesurer le flux de méthane, mais l'estimation de ces flux est compliquée par leur variabilité dans le temps et dans l'espace. Il y a aussi le mode de conduite du sol : ainsi par exemple, la mise en décharge des matières organiques peut provoquer d'importantes émissions de méthane, mais l'inverse quelques pratiques culturales comme le fumier et la fumure azotée entravent l'oxydation du méthane par les terres agricoles.

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Section: Techniques For Measuring Methanementioning

confidence: 99%

Soils as sources and sinks for atmospheric methane

Topp¹,

Pattey²

1997

Can. J. Soil. Sci.

192

115

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“…To define when (Z -d) >> zorn, the surface boundary layer can be divided into two regions: an upper inertial sublayer (Tennekes, 1973) in which the conventional flux-gradient relationships are valid, and a lower roughness sublayer (Raupach et al, 1980) immediately above the surface where the validity of the relationships is uncertain due to the proximity of the individual roughness elements. Cellier and Brunet (1992) found the thickness of the roughness sublayer, (Zw -d), where Zw is the upper height limit for the roughness sublayer, to scale with the lateral separation, 6, of the main roughness elements based on wind tunnel measurements (Raupach et al, 1980) and on studies over tree-covered savannah and pine forests (Garrat, 1980), African bushland (Chen and Schwerdtfeger, 1989), sugar cane (Cellier, 1986), and maize (Cellier and Brunet, 1992). As a rough approximation, this thickness (Zw -d) is about 3-46.…”

Section: Appendix Amentioning

confidence: 99%

Ambient biogenic hydrocarbons and isoprene emissions from a mixed deciduous forest

et al. 1996

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Experiments were conducted during the growing season of 1993 at a mixed deciduous forest in southern Ontario, Canada to investigate the atmospheric abundance of hydrocarbons from phytogenic origins, and to measure emission rates from foliage of deciduous trees. The most abundant phytogenic chemical species found in the ambient air were isoprene and the monoterpenes a-pinene and/3-pinene. Prior to leaf-bud break during spring, ambient hydrocarbon mixing ratios above the forest remained barely above instrument detection limit (~20 parts per trillion), but they became abundant during the latter part of the growing season. Peak isoprene mixing ratios reached nearly 10 parts per billion (ppbv) during mid-growing season while maximum monoterpene mixing ratios were close to 2 ppbv. Both isoprene and monoterpene mixing ratios exhibited marked diurnal variations. Typical isoprene mixing ratios were highest during mid-afternoon and were lowest during nighttime. Peak isoprene mixing ratios coincided with maximum canopy temperature. The diurnal pattern of ambient isoprene mixing ratio was closely linked to the local emissions from foliage. Isoprene emission rates from foliage were measured by enclosing branches of trees inside environmentcontrolled cuvette systems and measuring the gas mixing ratio difference between cuvette inlet and outlet airstream. Isoprene emissions depended on tree species, foliage ontogeny, and environmental factors such as foliage temperature and intercepted photosynthetically active radiation (PAR). For instance, young (< 1 month old) aspen leaves released approximately 80 times less isoprene than mature (> 3 months old) leaves. During the latter part of the growing season the amount of carbon released back to the atmosphere as isoprene by big-tooth and trembling aspen leaves accounted for approximately 2% of the photosynthetically fixed carbon. Significant isoprene mixing ratio gradients existed between the forest crown and at twice canopy height above the ground. The gradient diffusion approach coupled with similarity theory was used to estimate canopy isoprene flux densities. These canopy fluxes compared favorably with values obtained from a multilayered canopy model that utilized locally measured plant microclimate, biomass distribution and leaf isoprene emission rate data. Modeled isoprene fluxes were approximately 30% higher compared to measured fluxes. Further comparisons between measured and modeled canopy biogenic hydrocarbon flux densities are required to assess uncertainties in modeling systems that provide inventories of biogenic hydrocarbons.

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“…Thorn et al (1975) were among the first to point out the difficulties encountered in the application of standard fluxprofile relationships above forests. Many subsequent studies (e.g., Garratt, 1978Garratt, , 1979Garratt, , 1980Raupach, 1979;Denmead and Bradley, 1985;Cellier, 1986;Chen and Schwerdffeger, 1989) have confirmed that profiles measured near a forest canopy are not well described by the standard surface-layer similarity functions.…”

Section: Introductionmentioning

confidence: 97%

Regional shear stress of broken forest from radiosonde wind profiles in the unstable surface layer

Parlange

Brutsaert

1993

Boundary-Layer Meteorol

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Abstract. Mean wind speed profiles were measured by tracking radiosondes in the unstable atmospheric boundary layer (ABL) over the forested Landes region in southwestern France. New Monin-Obukhov stability correction functions, recently proposed following an analysis by Kader and Yaglom, as well as the Businger-Dyer stability formulation were tested, with wind speeds in the surface sublayer to calculate the regional shear stress. These profile-derived shear stresses were compared with eddy correlation measurements gathered above a mature forest stand at a location roughly 4.5 km from the radiosonde launch site. The shear stress values obtained by means of the newly proposed stability function were in slightly better agreement with the eddy correlation values than those obtained by means of a Businger-Dyer type stability function. The general robustness of the profile method can be attributed in part to prior knowledge of the regional surface roughness (z0 = 1.2 m) and the momentum displacement height (do = 6.0 m), which were determined from neutral wind profile analysis. The 100 m drag coefficient for the unstable conditions above this broken forest surface was found to be u2./V2oo = 0.0173.

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On the validity of flux-gradient relationships above very rough surfaces

Cited by 27 publications

References 11 publications

Soils as sources and sinks for atmospheric methane

Soils as sources and sinks for atmospheric methane

Ambient biogenic hydrocarbons and isoprene emissions from a mixed deciduous forest

Regional shear stress of broken forest from radiosonde wind profiles in the unstable surface layer

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