A Higher Order Closure Model for Canopy Flow

Wilson, Norman Robert; Shaw, Roger H.

doi:10.1175/1520-0450(1977)016<1197:ahocmf>2.0.co;2

Cited by 507 publications

(402 citation statements)

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“…Theoretically, a secondary wind speed maximum occurs, in a horizontally homogeneous canopy in uniform terrain, when the net convergence of the vertical flux of momentum transfer (am/Jz) exceeds the pressure destruction term in the w)uI budget (Shaw, 1976;Wilson and Shaw, 1977;Meyers and Paw U, 1986). We cannot conclude that the secondary wind speed maximum is not an artifact of the complexity of the local terrain and the heterogeneity of the natural canopy.…”

Section: Data Processingmentioning

confidence: 99%

“…In the past decade, many theoretical advances have been made, regarding the description of turbulence transfer in plant canopies, using higher-order closure and Lagrangian models (e.g., Shaw, 1976;Wilson and Shaw, 1977;Wilson et& 1981;Raupach and Shaw, 1982;Finnigan, 1985;Meyers and Paw U, 1986;Raupach, 1987). Unfortunately, little of the available within-canopy wind data is adequate to test and improve these models since much of these data consists only of measurements of mean scalar wind speed (e.g., Landsberg and James, 1971;Kalma and Stanhill, 1972).…”

Section: Introductionmentioning

confidence: 99%

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Turbulence structure in a deciduous forest

Baldocchi

Meyers

1988

Boundary-Layer Meteorol

220

125

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Abstract. Three-dimensional wind velocity components were measured at two levels above and at six levels within a fully-leafed deciduous forest. Greatest shear occurs in the upper 20% of the canopy, where over 70% of the foliage is concentrated. The turbulence structure inside the canopy is characterized as non-Gaussian, intermittant and highly turbulent. This feature is supported by large turbulence intensities, skewness and kurtosis values and by the large infrequent sweeps and ejections that dominate tangential momentum transfer. Considerable day/night differences were observed in the vertical protiles of the mean streamwise wind velocity and turbulence intensities since the stability of the nocturnal boundary layer dampens turbulence above and within the canopy.

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Section: Data Processingmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Turbulence structure in a deciduous forest

Baldocchi

Meyers

1988

Boundary-Layer Meteorol

220

125

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“…The flow statistics hw 0 w 0 i, hw 0 w 0 w 0 i and s can be estimated from secondorder closure principles such as the momentum transport model proposed by Wilson and Shaw [41]. Finally (6) can be numerically solved for hw 0 c 0 i, which upon differentiation with respect to z, results in S c .…”

Section: Eulerian Inverse Model (Eul)mentioning

confidence: 99%

“…In this implementation the D ij matrix is calculated by following the trajectory of an ensemble of fluid parcels, using the random walk algorithm of Thompson [38], released uniformly from a unit source placed at each jth layer. Like EUL and HEL, Wilson and ShawÕs [41] second-order closure model provides the required velocity statistics for the calculation of scalar dispersion. We emphasize that both forward and inverse calculations adopted the same flow statistics, and hence, differences between them cannot be attributed to the specification of the flow field.…”

Section: Canveg Fwdmentioning

confidence: 99%

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Quantifying net ecosystem exchange by multilevel ecophysiological and turbulent transport models

Siqueira

Katul

Lai

2002

Advances in Water Resources

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To quantify the interplay between scalar sources and sinks (S c ) and net ecosystem exchange (NEE), ''forward'' and ''inverse'' approaches have been proposed. The canonical form of forward approaches is a one-dimensional ecophysiological-radiative transfer scheme coupled to turbulent transport theory. In contrast, inverse approaches strictly rely on turbulent transport theory and mean scalar concentration as their primary input to infer S c and NEE. While the formulation of both approaches have evolved over the past decade, no systematic comparison between them was undertaken for the same data set, and over a wide range of atmospheric conditions. Our objective is to compare the predicted S c and NEE from these two approaches with eddy-covariance measurements. The results show that the forward method outperformed all three inverse methods for unstable and neutral conditions on short time scales ($30 min) but yielded comparable results at longer time scales. Poor agreement was obtained under stable conditions for all models. Hence, for modeling event-based flux variations, forward models are preferred. Since the forward method requires detailed knowledge of ecophysiological, drag, radiative transfer and other canopy attributes, all of which are difficult to obtain on a routine basis, a symbiotic use of forward and inverse approaches is most advantageous.

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Aeolian processes across transverse dunes. I: Modelling the air flow

Boxel

Arens

Dijk

1999

Earth Surf. Process. Landforms

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This paper discusses a two-dimensional second-order closure model simulating air flow and turbulence across transverse dunes. Input parameters are upwind wind speed, topography of the dune ridge and surface roughness distribution over the ridge. The most important output is the distribution of the friction velocity over the surface. This model is dynamically linked to a model that calculates sand transport rates and the resulting changes in elevation. The sand transport model is discussed in a separate paper.The simulated wind speeds resemble patterns observed during field experiments. Despite the increased wind speed over the crest, the friction velocity at the crest of a bare dune is reduced compared to the upstream value, because of the effect of stream line curvature on turbulence. These curvature effects explain why desert dunes can grow in height. In order to obtain realistic predictions of friction velocity it was essential to include equations for the turbulent variables in the model. In these equations streamline curvature is an important parameter.The main flaw of the model is that it cannot deal with flow separation and the resulting recirculation vortex. As a result, the increase of the wind speed and friction velocity after a steep dune or a slipface will be too close to the dune foot. In the sand transport model this was overcome by defining a separation zone.

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A Higher Order Closure Model for Canopy Flow

Cited by 507 publications

References 0 publications

Turbulence structure in a deciduous forest

Turbulence structure in a deciduous forest

Quantifying net ecosystem exchange by multilevel ecophysiological and turbulent transport models

Aeolian processes across transverse dunes. I: Modelling the air flow

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