Regional roughness of the landes forest and surface shear stress under neutral conditions

Parlange, Marc B.; Brutsaert, Wilfried

doi:10.1007/bf00121783

Cited by 67 publications

(32 citation statements)

References 18 publications

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“…These results were compared with previous studies; this shows that the lower limits of the log-range can be scaled with roughness, but that in the present case the upper limits is probably best scaled with either roughness or the inversion height. References: a Parlange and Brutsaert (1989); ; C Hiyama et al (1996) determined with tower measurements; d Parlange and Katul (1995) determined with tethersonde measurements. Fig.…”

Section: Discussionmentioning

confidence: 99%

Observations of Neutral Profiles of Wind Speed and Specific Humidity Above a Gently Rolling Landsurface

Asanuma

Dias²,

Kustas

et al. 2000

Journal of the Meteorological Society of Japan

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Analyses were made of wind speed and specific humidity profiles under neutral conditions obtained by radiosoundings over the gently rolling terrain of the Little Washita Basin, Oklahoma. Inspection of the wind speed profiles showed that the regional (scale of 1 to 10km) roughness of this basin was z0=0.45 f 0.21m, while the displacement height, do, was found to be 8.9m. The logarithmic layer of wind speed was observed to occupy the range, (38f43)z.<(z-d0)<(297+147)z0 or (0.15+0.10)h where hi is the height of the bottom of the capping inversion. This result is comparable with those of previous investigations for the lower limit of the range; however, this result also suggests that over this terrain hi is the relevant length scale for the upper limit. Evaporation values at the regional scale were computed by combining the wind speed profiles with the specific humidity profiles. Comparison with surface flux measurements at Bowen ratio ground stations supports the idea that profiles in the neutral atmospheric surface layer aloft at around 100m above the ground are conditioned by upwind surface characteristics at the meso-7 scale.

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Section: Discussionmentioning

confidence: 99%

Observations of Neutral Profiles of Wind Speed and Specific Humidity Above a Gently Rolling Landsurface

Asanuma

Dias²,

Kustas

et al. 2000

Journal of the Meteorological Society of Japan

Self Cite

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“…Due to its low sampling frequency, the SODAR/RASS cannot take the turbulence measurements needed to quantify stability by means of the Obukhov length (2). An alternative means to assess the stability of the atmosphere is the gradient Richardson number Ri g defined as Near-neutral atmospheric profiles are typically found when strong winds (high mechanical shear) and cloudy conditions (low surface heating) are observed; however, those conditions tend to be infrequent [37,46]. In this study, no distinction is made between the so-called "truly neutral" and the "conventionally neutral" atmospheric layers as discussed by Zilitinkevich and Esau [54].…”

Section: Determination Of the Momentum Surface Roughnessmentioning

confidence: 99%

Estimation of urban sensible heat flux using a dense wireless network of observations

et al. 2009

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The determination of the sensible heat flux over urban terrain is challenging due to irregular surface geometry and surface types. To address this, in 2006-07, a major field campaign (LUCE) took place at the École Polytechnique Fédérale de Lausanne campus, a moderately occupied urban site. A distributed network of 92 wireless weather stations was combined with routine atmospheric profiling, offering high temporal and spatial resolution meteorological measurements. The objective of this study is to estimate the sensible heat flux over the built environment under convective conditions. Calculations were based on Monin-Obukhov similarity for temperature in the surface layer. The results illustrate a good agreement between the sensible heat flux inferred from the thermal roughness length approach and independent calibrated measurements from a scintillometer located inside the urban canopy. It also shows that using only one well-selected station can provide a good estimate of the sensible heat flux over the campus for convective conditions. Overall, this

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“…where z o is the momentum roughness length for the canopy, which is about 0.08-0.18h (Parlange and Brutsaert, 1989), Dz is the computational grid node spacing (discussed later), and the similarity coefficients A u , A v , and A w are assumed constant independent of height and can be determined from their values for neutral ASL flows. From standard ASL flow experiments (Garratt, 1992), these coefficients are approximately given by…”

Section: Closure Constant Valuementioning

confidence: 99%

ONE- and TWO-Equation Models for Canopy Turbulence

Katul

Mahrt

Poggi

et al. 2004

Boundary-Layer Meteorology

344

223

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Abstract. The predictive skills of single-and two-equation (or K-e) models to compute profiles of mean velocity (U), turbulent kinetic energy (K), and Reynolds stresses ðu 0 w 0 Þ are compared against datasets collected in eight vegetation types and in a flume experiment. These datasets range in canopy height h from 0.12 to 23 m, and range in leaf area index (LAI) from 2 to 10 m 2 m À2 . We found that for all datasets and for both closure models, measured and modelled U, K, and u 0 w 0 agree well when the mixing length (l m ) is a priori specified. In fact, the root-mean squared error between measured and modelled U, K, and u 0 w 0 is no worse than published values for second-and third-order closure approaches. Within the context of onedimensional modelling, there is no clear advantage to including a turbulent kinetic dissipation rate (e) budget when l m can be specified instead. The broader implication is that the added complexity introduced by the e budget in K-e models need not translate into improved predictive skills of U, K, and u 0 w 0 profiles when compared to single-equation models.

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Regional roughness of the landes forest and surface shear stress under neutral conditions

Cited by 67 publications

References 18 publications

Observations of Neutral Profiles of Wind Speed and Specific Humidity Above a Gently Rolling Landsurface

Observations of Neutral Profiles of Wind Speed and Specific Humidity Above a Gently Rolling Landsurface

Estimation of urban sensible heat flux using a dense wireless network of observations

ONE- and TWO-Equation Models for Canopy Turbulence

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