Scalar Concentration Profiles in the Canopy and Roughness Sublayer

Harman, Ian N.; Finnigan, John

doi:10.1007/s10546-008-9328-4

Cited by 126 publications

(86 citation statements)

References 52 publications

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“…The black filled cycles are the measurements and red open circles are the inferred concentrations by the "x/NO y " ratio method (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.). atmospheric surface layer, it is only valid well above the rough surface (Högström, 1996) and fails in the so-called roughness sublayer, which is above tall canopies and within canopies (e.g., Harman and Finnigan, 2008). Simply adjusting parameters such as z 0 used in MOST may not solve this fundamental problem, and future work to improve the models will involve the use of vertically-varying profiles of mean scalar concentration (e.g., Harman and Finnigan, 2008) or a multi-layer canopy model that explicitly resolves the radiative, dynamical, and thermal transport within vegetation canopies.…”

Section: Evaluation Of Modeled V D (No Y )mentioning

confidence: 99%

Evaluating the calculated dry deposition velocities of reactive nitrogen oxides and ozone from two community models over a temperate deciduous forest

Wang

Chen

et al. 2011

Atmospheric Environment

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Evaluating the calculated dry deposition velocities of reactive nitrogen oxides and ozone from two community models over a temperate deciduous forest ) is very sensitive to the minimum canopy stomatal resistance (R i ) which is specified for each seasonal category assigned in WDDM. Treating Sep-Oct as autumn in WDDM for this deciduous forest site caused a large underprediction of V d (O 3 ) due to the leafless assumption in 'autumn' seasonal category for which an infinite R i was assigned. Reducing R i to a value of 70 s m À1 , the same as the default value for the summer season category, the modeled and measured V d (O 3 ) agreed reasonably well. HNO 3 was found to dominate the NO y flux during the measurement period; thus the modeled V d (NO y ) was mainly controlled by the aerodynamic and quasi-laminar sublayer resistances (R a and R b ), both being sensitive to the surface roughness length (z 0 ). Using an appropriate value for z 0 (10% of canopy height), WDDM and Noah-GEM agreed well with the observed daytime V d (NO y ). The differences in V d (HNO 3 ) between WDDM and Noah-GEM were small due to the small differences in the calculated R a and R b between the two models; however, the differences in R c of NO 2 and PAN between the two models reached a factor of 1.1e1.5, which in turn caused a factor of 1.1e1.3 differences for V d . Combining the measured concentrations and modeled V d , NO x , PAN and HNO 3 accounted for 19%, 4%, and 70% of the measured NO y fluxes, respectively.

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Section: Evaluation Of Modeled V D (No Y )mentioning

confidence: 99%

Evaluating the calculated dry deposition velocities of reactive nitrogen oxides and ozone from two community models over a temperate deciduous forest

Wang

Chen

et al. 2011

Atmospheric Environment

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“…This particular small hill, where vertical advection is significant, is likely to be an extreme case, however this 35 variability in the Schmidt number potentially makes modelling of tracer transport using mixing length closure schemes difficult. It would be possible to devise a scheme where Sc scaled with height to match results over flat ground, as done in Harman and Finnigan (2008), however these results suggest that even this approach might not be sufficient over hills. Having said all this it is then perhaps surprising that the tracer profiles from the one-and-a-half order model agree so well with those from the LES in figure 1.…”

Section: The Turbulent Schmidt Numbermentioning

confidence: 99%

“…There are also questions about the behaviour of the turbulent Schmidt number (the ratio of the turbulent diffusivities for momentum and scalars) within and just above the canopy (see e.g. Harman and Finnigan, 2008).…”

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confidence: 99%

Scalar Transport over Forested Hills

Ross

2011

Boundary-Layer Meteorol

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Numerical simulations of scalar transport in neutral flow over forested ridges are performed using both a one-and-a-half order mixing length closure scheme and a large-eddy simulation (LES). Such scalar transport (particularly of CO 2 ) has been a significant motivation for dynamical studies of forest canopy -atmosphere interactions. Results from the one-and-a-half order mixing length simulations show that hills where there is significant mean flow into and out of the canopy are more efficient at transporting scalars from the canopy to the boundary layer above. For the case with a source in the canopy this leads to lower mean concentrations of tracer within the canopy, although they can be very large horizontal variations over the hill. These

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“…Turbulent mixing is the fundamental driver in the exchange of mass, momentum and scalars between a forest canopy and the atmosphere (Finnigan et al, 2009;Harman and Finnigan, 2008). Quantifying these turbulent processes is necessary to understand the surface energy budget (Oncley et al, 2007), the global carbon budget (Law et al, 2002) and the fate of reactive trace gas species (Holzinger et al, 2005;Sörgel et al, 2011).…”

Section: Introductionmentioning

confidence: 99%

Analysis of coherent structures and atmosphere-canopy coupling strength during the CABINEX field campaign

et al. 2011

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Abstract. Intermittent coherent structures can be responsible for a large fraction of the exchange between a forest canopy and the atmosphere. Quantifying their contribution to momentum and heat fluxes is necessary to interpret measurements of trace gases and aerosols within and above forest canopies. The primary objective of the Community Atmosphere-Biosphere Interactions Experiment (CABINEX) field campaign (10 July 2009 to 9 August 2009) was to study the chemistry of volatile organic compounds (VOC) within and above a forest canopy. In this manuscript we provide an analysis of coherent structures and canopy-atmosphere exchange during CABINEX to support in-canopy gradient measurements of VOC. We quantify the number and duration of coherent structure events and their percent contribution to momentum and heat fluxes with two methods: (1) quadrant-hole analysis, and (2) wavelet analysis. Despite differences in the duration and number of events, both methods predict that coherent structures contribute 40-50 % to momentum fluxes and 44-65 % to heat fluxes during the CABINEX campaign. Contributions associated with coherent structures are slightly greater under stable atmospheric conditions. By comparing heat fluxes within and above the canopy, we determine the degree of coupling between upper canopy and atmosphere, and find that they are coupled the majority of the time. Uncoupled canopyatmosphere events occur in the early morning (4-8 a.m. local time) approximately 30 % of the time. This study conCorrespondence to: A. L. Steiner (alsteiner@umich.edu) firms that coherent structures contribute significantly to the exchange of heat and momentum between the canopy and atmosphere at the CABINEX site, and indicates the need to include these transport processes when studying the mixing and chemical reactions of trace gases and aerosols between a forest canopy and the atmosphere.

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Scalar Concentration Profiles in the Canopy and Roughness Sublayer

Cited by 126 publications

References 52 publications

Evaluating the calculated dry deposition velocities of reactive nitrogen oxides and ozone from two community models over a temperate deciduous forest

Evaluating the calculated dry deposition velocities of reactive nitrogen oxides and ozone from two community models over a temperate deciduous forest

Scalar Transport over Forested Hills

Analysis of coherent structures and atmosphere-canopy coupling strength during the CABINEX field campaign

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