Profiles and fluxes of micrometeorological parameters above and within the Mediterranean forest at Castelporziano

Schween, Jan H.; Zelger, M.; Wichura, Bodo; Fokem, Thomas; Dlugi, R.

doi:10.1016/s1352-2310(97)00113-1

Cited by 15 publications

(2 citation statements)

References 32 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Cellier and Brunet (1992) propose a dimensionless factor γ to account for the increase in turbulent diffusivity. Following this suggestion, Schween et al (1997), using data measured over a 12 m tall oak and pine tree forest, found γ θ = 2.2. They pointed out that the different behavior in the RSL may be due to flux originating below the zero-plane displacement height, since in-canopy air may have significantly different characteristics from above-canopy air.…”

Section: Introductionmentioning

confidence: 90%

Scalar turbulent behavior in the roughness sublayer of an Amazonian forest

Zahn¹,

Dias²,

Araújo³

et al. 2016

Atmos. Chem. Phys.

View full text Add to dashboard Cite

Abstract. An important current problem in micrometeorology is the characterization of turbulence in the roughness sublayer (RSL), where most of the measurements above tall forests are made. There, scalar turbulent fluctuations display significant departures from the predictions of MoninObukhov similarity theory (MOST). In this work, we analyze turbulence data of virtual temperature, carbon dioxide, and water vapor in the RSL above an Amazonian forest (with a canopy height of 40 m), measured at 39.4 and 81.6 m above the ground under unstable conditions. We found that dimensionless statistics related to the rate of dissipation of turbulence kinetic energy (TKE) and the scalar variance display significant departures from MOST as expected, whereas the vertical velocity variance follows MOST much more closely. Much better agreement between the dimensionless statistics with the Obukhov similarity variable, however, was found for the subset of measurements made at a low zenith angle Z, in the range 0 • < |Z| < 20 • . We conjecture that this improvement is due to the relationship between sunlight incidence and the "activation-deactivation" of scalar sinks and sources vertically distributed in the forest. Finally, we evaluated the relaxation coefficient of relaxed eddy accumulation: it is also affected by zenith angle, with considerable improvement in the range 0 • < |Z| < 20 • , and its values fall within the range reported in the literature for the unstable surface layer. In general, our results indicate the possibility of better stability-derived flux estimates for low zenith angle ranges.

show abstract

Section: Introductionmentioning

confidence: 90%

Scalar turbulent behavior in the roughness sublayer of an Amazonian forest

Zahn¹,

Dias²,

Araújo³

et al. 2016

Atmos. Chem. Phys.

View full text Add to dashboard Cite

show abstract

“…There are particular problems in applying microclimatological models of flux ± profile relations to forested landscapes, due to their large aerodynamic roughness: some of these issues are investigated by Bosveld (1997), Mahrt et al (1997), Schween et al (1997) and Wenzel et al (1997). Integrated studies of energy and mass exchanges at the forest crown top are represented by Arado Â ttir et al Ogunjemiyo et al (1997), Oncley et al (1997 and Vidale et al (1997).…”

Section: Forested Landscapesmentioning

confidence: 99%