Pseudo-wavelet analysis of turbulence patterns in three vegetation layers

Qiu, Jie; U, Kyaw Tha Paw; Shaw, Roger H.

doi:10.1007/bf00712394

Cited by 59 publications

(34 citation statements)

References 22 publications

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“…This is in agreement with Qiu et al, 36 who applied pseudo-wavelet analysis for coherent structure identi®cation for¯ow over a maize ®eld under similar meteorological conditions. They found the same principal time scale for the vertical velocities (about 15 s) at the top of the canopy.…”

Section: Donoho and Johnstone's Local Methodssupporting

confidence: 91%

“…When viewed in this way, turbulent¯ows are comprised of a superposition of organized, coherent structures and disorganized, or`r andom'' background activity 21,43 . Coherent structures in the atmosphere can be so markedly developed that they are clearly identi®able in measured time series as``ramps'' arising from the sweepejection motion in the surface layer 1,16,17,19,27,36,43 . Gao et al, 16,17 identi®ed coherent structures above a forest canopy having regularly repeated organized cycles of ejection-like upward¯ow and the subsequent sweep-like descending motions.…”

Section: Introductionmentioning

confidence: 99%

“…Most methods proposed to identify coherent structure properties have subjective components 2,3,5,14,20,27,36,37,39,40 . For example, an arbitrary threshold value is set for the wavelet coecients when selecting organized events, or the size of a certain window employed in the analysis must be speci®ed.…”

Section: Introductionmentioning

confidence: 99%

“…Prior to analysis, the 21 Hz measurements were block averaged to 1 Hz, since the principal time scales of the coherent structures are expected to be at least an order of magnitude greater than 1 second 19,36 . As a result, the original 20 min data sets were reduced to 1024 ( 2 10 ) data points.…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

An objective method for determining principal time scales of coherent eddy structures using orthonormal wavelets

Szilágyi

Parlange

Katul

et al. 1999

Advances in Water Resources

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A new, parameter-free method, based on orthonormal wavelet expansions is proposed for calculating the principal time scale of coherent structures in atmospheric surface layer measurements. These organized events play an important role in the exchange of heat, mass, and momentum between the land and the atmosphere. This global technique decomposes the energy contribution at each scale into organized and random eddy motion. The method is demonstrated on vertical wind velocity measurements above bare and vegetated surfaces. It is found to give nearly identical results to a local thresholding approach developed for signal de-noising that assigns the wavelet coecients to organized and random motion. The eect of applying anti-and/or near-symmetrical wavelet basis functions is also investigated. Ó

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Section: Donoho and Johnstone's Local Methodssupporting

confidence: 91%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

An objective method for determining principal time scales of coherent eddy structures using orthonormal wavelets

Szilágyi

Parlange

Katul

et al. 1999

Advances in Water Resources

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“…The Mexican hat is popular for its good sensitivity to 'see' the ramp-like or saw-tooth pattern, so-called isolated sharp step change of the signal ( [12], [13]). These patterns were detected in velocity or scalar time-series measured in-situ above a plant canopy like a forrest, an orchard or a cereal field.…”

Section: Wavelet Analysismentioning

confidence: 99%

Wavelet analysis of the turbulent flow over the very rough surface

Kellnerová

Kukačka

Nosek

et al. 2014

EPJ Web of Conferences

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Abstract. Wavelet analysis is applied to data from PIV measurement in order to recognize a specific structure in the flow. The PIV snaphots achieved on the model of the street canyon was used as a test case. Four flow characteristics that are at disposal from one-point simultaneous two-components measurement (e.g. from 2D LDA) were analyzed by Wavelet method: longitudinal and vertical velocity, momentum flux u'w' and δS -the difference between momentum fluxes associated with a sweep and an ejection. Each of characteristic is useful for detection of certain type of event. We have focused on the sweep and the ejection that seem to be the most convenient for investigation of a significant inflow or an outflow from the street canyon.

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Combining the bulk transfer formulation and surface renewal analysis for estimating the sensible heat flux without involving the parameter

Castellvı́

Jiménez-Gavilán

González‐Dugo

2014

Water Resources Research

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The single-source bulk transfer formulation (based on the Monin-Obukhov Similarity Theory, MOST) has been used to estimate the sensible heat flux, H, in the framework of remote sensing over homogeneous surfaces (H MOST ). The latter involves the canopy parameter, kB 21 , which is difficult to parameterize. Over short and dense grass at a site influenced by regional advection of sensible heat flux, H MOST with kB 21 5 2 (i.e., the value recommended) correlated strongly with the H measured using the Eddy Covariance, EC, method, H EC . However, it overestimated H EC by 50% under stable conditions for samples showing a local air temperature gradient larger than the measurement error, 0.4 km 21 . Combining MOST and Surface Renewal analysis, three methods of estimating H that avoid kB 21 dependency have been derived. These new expressions explain the variability of H versus u Ã T c 2T ðzÞ À Á , where u Ã is the friction velocity, T c is the radiometric surface temperature, and T ðzÞ is the air temperature at height, z. At two measurement heights, the three methods performed excellently. One of the methods developed required the same readily/commonly available inputs as H MOST due to the fact that the ratio between T c 2T ðzÞ À Á and the ramp amplitude was found fairly constant under stable and unstable cases. Over homogeneous canopies, at a site influenced by regional advection of sensible heat flux, the methods proposed are an alternative to the traditional bulk transfer method because they are reliable, exempt of calibration against the EC method, and are comparable or identical in cost of application. It is suggested that the methodology may be useful over bare soil and sparse vegetation.

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Pseudo-wavelet analysis of turbulence patterns in three vegetation layers

Cited by 59 publications

References 22 publications

An objective method for determining principal time scales of coherent eddy structures using orthonormal wavelets

An objective method for determining principal time scales of coherent eddy structures using orthonormal wavelets

Wavelet analysis of the turbulent flow over the very rough surface

Combining the bulk transfer formulation and surface renewal analysis for estimating the sensible heat flux without involving the parameter

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