Molecular dissipation of turbulent fluctuations in the convective mixed layer part I: Height variations of dissipation rates

Guillemet, B.; Isaka, Harumi; Mascart, Patrick

doi:10.1007/bf00239611

Cited by 26 publications

(19 citation statements)

References 21 publications

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“…This decrease seems mostly realistic since the horizontal scales of w decrease rapidly with height progressing downwards below z/% N 0.25. Our present values of dimensionless dissipation are similar to those of Guillemet et al (1983) which lay near 0.65 at z/h = 0.2 and decreased to about 0.25 at z/h = 1. The present TKE balance agrees well with that of Lenschow et al (1980) except that term IV here does not become positive again in the upper mixed layer.…”

Section: The Turbulence Kinetic Energy(tke)budgetsupporting

confidence: 76%

Further results from a laboratory model of the convective planetary boundary layer

Deardorff

Willis

1985

Boundary-Layer Meteorol

193

115

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The turbulence in a laboratory convective mixed layer is probed more extensively than in the preliminary study of Willis and Deardorff (1974), and results presented. Turbulence intensities, spectra and probability distributions using mixed-layer scaling compare favorably with similarly scaled field measurements not available or plentiful in 1974. However, the velocity spectra in the convection tank exhibit only a short inertial subrange due to the close proximity of the dissipation subrange to the energy-containing range.The turbulence budget suggests that the convergence of the vertical transport of pressure fluctuations is a rather important term.Results on the entrainment rate are also presented, using both mixed-layer scaling and local interfacial scaling.

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Section: The Turbulence Kinetic Energy(tke)budgetsupporting

confidence: 76%

Further results from a laboratory model of the convective planetary boundary layer

Deardorff

Willis

1985

Boundary-Layer Meteorol

193

115

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“…Our data show a rapid decrease of E* with height, up to ZlzisO.2, then an almost constant value at about 0.24, right up to z G 0.8 Zi which is the highest level in our data set. In this way, Guillemet et al (1983), and Caughey and Palmer (1979) have obtained similarly constant results, but with large values. For the bulk of the mid-section of the mixed layer, the data of Guillemet et al are between 0.35 and 0.65, while the data of Caughey and Palmer are between about 0.51 and 0.77, as shown in Figure 6(a).…”

Section: Peak Wavelengthsmentioning

confidence: 53%

“…However, our value of A, = 0.5, obtained by eye-fitting the data points, is smaller than the 0.9 value given by Guillemet et al (1983).…”

Section: Peak Wavelengthsmentioning

confidence: 65%

“…Also, in the lower levels (Z/Z, < 0.5), our data seem to agree fairly well with the (zl~~)-~'~ law predicted under the local free convection similarity hypothesis (Wyngaard, 1973). The dashed line in Figure 6 The present value of A0 is somewhat smaller than the 0.55 value given by Guillemet et al (1983).…”

Section: Peak Wavelengthsmentioning

confidence: 86%

“…In a steady convective mixed layer, it has been amply shown (Deardorff, 1970;Kaimal et al, 1976;Wyngaard et al, 1978;Guillemet et al, 1983;etc. ) that the appropriate scaling factors are (for notation, see Appendix)…”

Section: Factorsmentioning

confidence: 99%

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Some turbulence characteristics of convectively mixed layers over rugged and homogeneous terrain

Huynh

Coulman

Turner

1990

Boundary-Layer Meteorol

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Turbulence characteristics of convectively mixed layers over rugged and homogenous terrain are presented, and their differences are sought. The data used in the study were obtained from aircraftborne instruments.Apart from statistics related to the mixing ratio q, there does not seem to be a marked difference between the two sets of data. This lack of difference is attributed to the degree of ruggedness of the terrain and the dominant wind direction. The behaviour of some statistics related to q is attributed to the entrainment effect of the unstable layer of the moist, cool air above the mixed layer.

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Boundary‐layer moisture regimes

Mahrt

1991

Quart J Royal Meteoro Soc

117

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Data from fifty-two aircraft flight legs 10C-150m above ground from HAPEX and FIFE are analysed to estimate characteristics of boundary-layer moisture fluctuations in boundary layers with different bulk stability and surface energy regimes. In HAPEX, considerable effort was devoted to the quality of measurement of moisture fluctuations. The data include repeated 120krn flight legs flown at 1. 50111 over the same relatively homogeneous terrain, allowing statistical examination of motion characteristics on horizontal scales up to 10 km.This study finds two prototype boundary-layer regimes. With significant boundary-layer instability, relatively weak surface evaporation and drier air aloft, the entrainment-drying boundary layer may develop. This boundary layer is characterized by vertical divergence of the moisture flux and significant diffusion of dry air from the top downwards (top-down). In this type of boundary layer, dry air occasionally reaches the lower boundary layer, leading to negative moisture skewness in spite of positive temperature and vertical velocity skewness associated with warm moist updraughts. In contrast, the moistening boundary layer associated with greater surface evaporation is characterized by positive moisture skewness near the surface.In addition to the above turbulent moisture fluctuations, some of the above data are characterized by 10 km moisture variations with horizontal gradients often concentrated in narrow zones of horizontal convergence. Since corresponding signatures of vertical velocity and temperature are weaker, these zones are referred to as 'mesoscale' moisture fronts. As a more general feature, moisture variations on scales of 5 km and greater are negatively correlated with temperature variations associated with cool moist regions and warm dry regions. On scales of tens of kilometres and greater, such negative correlation may be due to inhomogeneity of the surface energy budget. The negative moisture-temperature correlation leads to large mesoscale variations of relative humidity and the lifted condensation level.

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Molecular dissipation of turbulent fluctuations in the convective mixed layer part I: Height variations of dissipation rates

Cited by 26 publications

References 21 publications

Further results from a laboratory model of the convective planetary boundary layer

Further results from a laboratory model of the convective planetary boundary layer

Some turbulence characteristics of convectively mixed layers over rugged and homogeneous terrain

Boundary‐layer moisture regimes

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