Implications of Monin–Obukhov Similarity Theory for Scalar Quantities

Hill, R. J.

doi:10.1175/1520-0469(1989)046<2236:iomstf>2.0.co;2

Cited by 136 publications

(84 citation statements)

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“…A sufficient condition for this to happen, and the simplest although by no means a necessary condition, is the validity of the wellknown hypothesis of perfect similarity between scalars (Hill, 1989;Dias and Brutsaert, 1996), which often fails under unstable conditions due to phenomena originating above the surface layer and to the transport of scalar variance from above (Cancelli et al, 2012(Cancelli et al, , 2014. Furthermore, the physics of the roughness sublayer proper may complicate this picture even more.…”

Section: The Relaxed Eddy Accumulation Methods and Related Analysesmentioning

confidence: 99%

Scalar turbulent behavior in the roughness sublayer of an Amazonian forest

Zahn¹,

Dias²,

Araújo³

et al. 2016

Atmos. Chem. Phys.

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Abstract. An important current problem in micrometeorology is the characterization of turbulence in the roughness sublayer (RSL), where most of the measurements above tall forests are made. There, scalar turbulent fluctuations display significant departures from the predictions of MoninObukhov similarity theory (MOST). In this work, we analyze turbulence data of virtual temperature, carbon dioxide, and water vapor in the RSL above an Amazonian forest (with a canopy height of 40 m), measured at 39.4 and 81.6 m above the ground under unstable conditions. We found that dimensionless statistics related to the rate of dissipation of turbulence kinetic energy (TKE) and the scalar variance display significant departures from MOST as expected, whereas the vertical velocity variance follows MOST much more closely. Much better agreement between the dimensionless statistics with the Obukhov similarity variable, however, was found for the subset of measurements made at a low zenith angle Z, in the range 0 • < |Z| < 20 • . We conjecture that this improvement is due to the relationship between sunlight incidence and the "activation-deactivation" of scalar sinks and sources vertically distributed in the forest. Finally, we evaluated the relaxation coefficient of relaxed eddy accumulation: it is also affected by zenith angle, with considerable improvement in the range 0 • < |Z| < 20 • , and its values fall within the range reported in the literature for the unstable surface layer. In general, our results indicate the possibility of better stability-derived flux estimates for low zenith angle ranges.

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Section: The Relaxed Eddy Accumulation Methods and Related Analysesmentioning

confidence: 99%

Scalar turbulent behavior in the roughness sublayer of an Amazonian forest

Zahn¹,

Dias²,

Araújo³

et al. 2016

Atmos. Chem. Phys.

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“…Hill (1989) pointed out that, if the structure parameters all follow MOST, their similarity functions must be the same ( f T = f q ), and temperature and humidity must be perfectly correlated (i.e. correlation coefficient R T q = 1).…”

Section: Monin-obukhov Similarity Relationshipsmentioning

confidence: 99%

“…Measurements suggest that A T = 2.7 (Wyngaard et al 1971b;Kaimal et al 1976;Wyngaard and LeMone 1980;Kunkel et al 1981;Andreas 1991). While Wyngaard and LeMone (1980) suggested A q ≈ 1.5, Andreas (1991) proposed that A T = A q = 2.7 (when R T q = 1), referring to the study of Hill (1989). The previous LES study of Peltier and Wyngaard (1995) suggested A q = 2.0−2.7.…”

Section: Monin-obukhov Similarity Relationshipsmentioning

confidence: 99%

The Effect of Surface Heterogeneity on the Structure Parameters of Temperature and Specific Humidity: A Large-Eddy Simulation Case Study for the LITFASS-2003 Experiment

Maronga

Hartogensis

Raasch

et al. 2014

Boundary-Layer Meteorol

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We conduct a high-resolution large-eddy simulation (LES) case study in order to investigate the effects of surface heterogeneity on the (local) structure parameters of potential temperature C 2 T and specific humidity C 2 q in the convective boundary layer (CBL). The kilometre-scale heterogeneous land-use distribution as observed during the LITFASS-2003 experiment was prescribed at the surface of the LES model in order to simulate a realistic CBL development from the early morning until early afternoon. The surface patches are irregularly distributed and represent different land-use types that exhibit different roughness conditions as well as near-surface fluxes of sensible and latent heat. In the analysis, particular attention is given to the Monin-Obukhov similarity theory (MOST) relationships and local free convection (LFC) scaling for structure parameters in the surface layer, relating C 2 T and C 2 q to the surface fluxes of sensible and latent heat, respectively. Moreover we study possible effects of surface heterogeneity on scintillometer measurements that are usually performed in the surface layer. The LES data show that the local structure parameters reflect the surface heterogeneity pattern up to heights of 100-200 m. The assumption of a blending height, i.e. the height above the surface where the surface heterogeneity pattern is no longer visible in the structure parameters, is studied by means of a two-dimensional correlation analysis. We show that no such blending height is found at typical heights of scintillometer measurements for the studied case. Moreover, C 2 q does not follow MOST, which is ascribed to the entrainment of dry air at the top of the boundary layer. The application of MOST and LFC scaling to elevated C 2 T data still gives reliable estimates of the surface sensible heat flux. We show, however, that this flux, derived from scintillometer data, is only representative of the footprint area of the scintillometer, whose size depends strongly on the synoptic conditions.

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“…The structure parameter of the refractive index of air is related to C 2 T , C 2 q and C T q via (Hill 1989;Lüdi et al 2005;Ward et al 2013),…”

Section: From C 2 N To C 2 T : Corrections For Humidity Contributionmentioning

confidence: 99%

On the Discrepancy in Simultaneous Observations of the Structure Parameter of Temperature Using Scintillometers and Unmanned Aircraft

Braam

Beyrich

Bange

et al. 2015

Boundary-Layer Meteorol

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We elaborate on the preliminary results presented in Beyrich et al. (in BoundaryLayer Meteorol 144:83-112, 2012), who compared the structure parameter of temperature (C 2 T ) obtained with the unmanned meteorological mini aerial vehicle (M 2 AV) versus C 2 T obtained with two large-aperture scintillometers (LASs) for a limited dataset from one single experiment (LITFASS-2009). They found that C 2 T obtained from the M 2 AV data is significantly larger than that obtained from the LAS data. We investigate if similar differences can be found for the flights on the other six days during LITFASS-2009 and LITFASS-2010, and whether these differences can be reduced or explained through a more elaborate processing of both the LAS data and the M 2 AV data. This processing includes different corrections and measures to reduce the differences between the spatial and temporal averaging of the datasets. We conclude that the differences reported in Beyrich et al. can be found for other days as well. For the LAS-derived values the additional processing steps that have the largest effect are the saturation correction and the humidity correction. For the M 2 AV-derived values the most important step is the application of the scintillometer path-weighting function. Using the true air speed of the M 2 AV to convert from a temporal to a spatial structure function rather than the ground speed (as in Beyrich et al.) does not change the mean discrepancy, but it does affect C 2 T values for individual flights. M 2 AV data depends on the fact that the underlying temperature dataset combines spatial and temporal sampling, we used large-eddy simulation data to analyze C 2 T from virtual flights with different mean ground speeds. This analysis shows that C 2 T does only slightly depends on the true air speed when averaged over many flights.

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Implications of Monin–Obukhov Similarity Theory for Scalar Quantities

Cited by 136 publications

References 0 publications

Scalar turbulent behavior in the roughness sublayer of an Amazonian forest

Scalar turbulent behavior in the roughness sublayer of an Amazonian forest

The Effect of Surface Heterogeneity on the Structure Parameters of Temperature and Specific Humidity: A Large-Eddy Simulation Case Study for the LITFASS-2003 Experiment

On the Discrepancy in Simultaneous Observations of the Structure Parameter of Temperature Using Scintillometers and Unmanned Aircraft

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