An Advanced Method Based on Surface Renewal Theory to Estimate the Friction Velocity and the Surface Heat Flux

Castellvı́, F.

doi:10.1029/2018wr022808

Cited by 12 publications

(12 citation statements)

References 48 publications

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“…This is justified on the grounds that z 0 m is reasonably described from simplified two‐parameter models (e.g.,

λ_{f}, λ_{p}

), as confirmed here. For a variety of surfaces, including bluff‐rough surfaces, a relation of the form

z_{0 s} / z_{0 m} \sim R e_{*}^{n}

is used (Brutsaert, 1965; 1975b; Zilitinkevich et al ., 2001; Li et al ., 2017; Katul and Liu, 2017; Castellví, 2018). A variety of exponents ( n =0, 1/4 or 1/2) and intercepts have been reported across differing surfaces.…”

Section: Roughness Lengths Determined From Lesmentioning

confidence: 99%

Revisiting the relation between momentum and scalar roughness lengths of urban surfaces

Bou‐Zeid

Grimmond

et al. 2020

Quart J Royal Meteoro Soc

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Large‐Eddy Simulations (LESs) of neutral flow over regular arrays of cuboids are conducted to explore connections between momentum (z0m) and scalar (z0s) roughness lengths in urban environments, and how they are influenced by surface geometry. As LES resolves the obstacles but not the micro‐scale boundary layers attached to them, the aforementioned roughness lengths are analyzed at two distinct spatial scales. At the micro‐scale (roughness of individual facets, e.g., roofs), it is assumed that both momentum and scalar transfer are governed by accepted arguments for smooth walls that form the basis for the LES wall‐model. At the macro‐scale, the roughness lengths are representative of the aggregate effects of momentum and scalar transfer over the resolved roughness elements of the whole surface, and hence they are directly computed from the LES. The results indicate that morphologically based parametrizations for macro‐scale z0m are adequate overall. The relation between the momentum and scalar macro‐roughness values, as conventionally represented by log(z0m/z0s) and assumed to scale with Re∗n (where Re∗ is a roughness Reynolds number), is then interpreted using surface renewal theory (SRT). SRT predicts n = 1/4 when only Kolmogorov‐scale eddies dominate the scalar exchange, whereas n = 1/2 is predicted when large eddies limit the renewal dynamics. The latter is found to better capture the LES results. However, both scaling relations indicate that z0s decreases when z0m increases for typical urban geometries and scales. This is opposite to how their relation is usually modelled for urban canopies (i.e., z0s/z0m is a fixed value smaller than unity).

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“…This is justified on the grounds that z 0 m is reasonably described from simplified two‐parameter models (e.g.,

λ_{f}, λ_{p}

), as confirmed here. For a variety of surfaces, including bluff‐rough surfaces, a relation of the form

z_{0 s} / z_{0 m} \sim R e_{*}^{n}

Section: Roughness Lengths Determined From Lesmentioning

confidence: 99%

Revisiting the relation between momentum and scalar roughness lengths of urban surfaces

Bou‐Zeid

Grimmond

et al. 2020

Quart J Royal Meteoro Soc

View full text Add to dashboard Cite

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“…Likely, a two-dimensional sonic anemometer, provided that it allows recording the sonic temperature at high frequency, is the most convenient instrument to estimate H SR-P because it is robust and measures the wind speed with high precision. It allows estimating the ramp dimensions and the friction velocity using different methods [62,63]. When half-hourly latent heat flux accumulations are of interest, (R n − G − H SR-D ) appeared friendly because H SR-D performed as a method exempt of calibration (the errors nearly balanced the accumulated estimates of latent heat flux) and, currently, free-software is available to estimate the ramp dimensions [64].…”

Section: Discussionmentioning

confidence: 99%

Estimation of the Latent Heat Flux over Irrigated Short Fescue Grass for Different Fetches

Castellvı́

Jiménez-Gavilán

2021

Atmosphere

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Often in agrometeorology the instrumentation required to estimate turbulent surface fluxes must be installed at sites where fetch is not sufficient for a sector of wind directions. For different integrated flux-footprints (IFFP) thresholds and taking as a reference the half-hourly latent heat fluxes (LE) measured with a large weighing lysimeter (LELys), the eddy covariance (EC) method and two methods based on surface renewal (SR) analysis to estimate LE were tested over short fescue grass. One method combined SR with the flux-gradient (profile) relationship, SR-P method, and the other with the dissipation method, SR-D method. When LE was estimated using traces of air moisture, good performances were obtained using the EC and the SR-P methods for samples with IFFP higher than 85%. However, the closest LE estimates were obtained using the residual method. For IFFP higher than 50%, the residual method combined with the sensible heat flux estimates determined using the SR-P method performed close to LELys and using the SR-D method good estimates were obtained for accumulated LELys. To estimate the sensible heat flux, the SR-D method can be recommended for day-to-day use by farmers because it is friendly and affordable.

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“…By defining a macro parcel of air as a parcel of air which volume, per unit area, may cover all the sources of scalar at the surface, a coherent motion (regular eddy motion of macro parcels of air) is carried out by a coherent structure which is defined as an eddy capable to impose some organization in the turbulence in the surface layer. Thus, the ramp period accounts for the time that a macro parcel of air remained in contact with the surface and the ramp amplitude for the net temperature increase (for an unstable case) while it remained in contact with the surface [33][34][35].…”

Section: Sensible Heat Fluxmentioning

confidence: 99%

Sensible Heat and Latent Heat Flux Estimates in a Tall and Dense Forest Canopy under Unstable Conditions

Castellvı́

Buttar

et al. 2022

Atmosphere

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A method to estimate the sensible heat flux (H) for unstable atmospheric condition requiring measurements taken in half-hourly basis as input and involving the land surface temperature (LST), HLST, was tested over a tall and dense aspen stand. The method avoids the need to estimate the zero-plane displacement and the roughness length for momentum. The net radiation (Rn) and the latent heat flux (λE) dominated the surface energy balance (SEB). Therefore, λE was estimated applying the residual method using HLST as input, λER-LST. The sum of H and λE determined with the eddy covariance (EC) method led to a surface energy imbalance of 20% Rn. Thus, the reference taken for the comparisons were determined forcing the SEB using the EC Bowen ratio (BREB method). For clear sky days, HLST performed close to HBREB. Therefore, it showed potential in the framework of remote sensing because the input requirements are similar to current methods widely used. For cloudy days, HLST scattered HBREB and nearly matched the accumulated sensible hear flux. Regardless of the time basis and cloudiness, λER-LST was close to λEBREB. For all the data, both HLST and λER-LST were not biased and showed, respectively, a mean absolute relative error of 24.5% and 12.5% and an index of agreement of 68.5% and 80%.

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An Advanced Method Based on Surface Renewal Theory to Estimate the Friction Velocity and the Surface Heat Flux

Cited by 12 publications

References 48 publications

Revisiting the relation between momentum and scalar roughness lengths of urban surfaces

Revisiting the relation between momentum and scalar roughness lengths of urban surfaces

Estimation of the Latent Heat Flux over Irrigated Short Fescue Grass for Different Fetches

Sensible Heat and Latent Heat Flux Estimates in a Tall and Dense Forest Canopy under Unstable Conditions

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