Micrometeorological and PBL experiments in Australia

479

263

Some of the fundamental issues of surface layer meteorology are critically reviewed. For the von Karman constant (Ic), values covering the range from 0.32 to 0.65 have been repotted. Most of the data are, however, found in a rather narrow range between 0.39 and 0.4 1. Plotting all available atmospheric data against the so-called roughness Reynolds number, Rq, = U+Z~/Y or against the surface Rossby number, Roa = G/f .zo gives no clear indication of systematic trend. It is concluded that k is indeed constant in atmospheric surface-layer flow and that its value is the same as that found for laboratory flows, i.e. about 0.40.Various published formulae for non-dimensional wind and temperature profiles, &, and tih respectively, are compared after adjusting the fluxes so as to give k = 0.40 and (dh/&)z,L=O = 0.95. It is found that for Iz/LI 2 0.5 the various formulae agree to within lO-20%. For unstable stratification the various formulations for ~$h continue to agree within this degree of accuracy up to at least z/L z -2. For drn in very unstable conditions results are still conflicting. Several recent data sets agree that for unstable stratification Ri M lSz/ L up to at least -z/L = 0.5 and possibly well beyond.For the Kolmogorov streamwise inertial subrange constant, (Y ,,, it is concluded from an extensive data set that aU = 0.52 f 0.02. The corresponding constant for temperature is much more uncertain, its most probable value being, however, about 0.80, which is also the most likely value for the corresponding constant for humidity.The turbulence kinetic energy budget is reviewed. It is concluded that different data sets give conflicting results in important respects, particularly so in neutral conditions. It is demonstrated that the inertial-subrange method can give quite accurate estimates of the fluxes of momentum, sensible heat and water vapour from high frequency measurements of wind, temperature and specific humidity alone, provided 'apparent' values of the corresponding Kolmogorov constants are used. For temperature and humidity, the corresponding values turn out to be equal to the 'true' constants, so PA M p Z 0.80. For momentum, however, the apparent constant (Y,A z 0.60. * Based on an invited paper presented at

Section: Theorymentioning

confidence: 94%

Review of some basic characteristics of the atmospheric surface layer

Högström

1996

479

263

“…Following early work by Sheppard (1947) the surface stress was directly measured with a drag plate in Australia (Bradley, 1968), and the sensible and latent heat fluxes were measured with highly sensitive, modified classical sensors (Dyer et al, 1967). TABLE I Important micrometeorological experiments up to 1986(McBean et al, 1979Foken, 1990;Garratt and Hicks, 1990) Step Boundary-layer exp. Lettau (1957Lettau ( ) 1962 Kerang, Australia…”

Section: Historical Overviewmentioning

confidence: 99%

“…Step ITCE-1961Tsvang et al (1985) 1986 Lövsta, Sweden Grass Surface layer Högström (1990) These findings were the basis for many famous experiments (Table I), among them many prominent Australian experiments for studying turbulent exchange processes (Garratt and Hicks, 1990), the so-called intercomparison experiments for turbulence sensors (Miyake et al, 1971;Tsvang et al, 1973;Dyer et al, 1982;Tsvang et al, 1985), and finally the KANSAS 1968 experiment (Izumi, 1971;Kaimal and Wyngaard, 1990), which was the basis for the widely used universal functions of . An important state-of-the-art summary of turbulent exchange between the lower atmosphere and the surface was given in 1973 at the Workshop on Micrometeorology (Haugen, 1973).…”

Section: Historical Overviewmentioning

confidence: 99%

See 1 more Smart Citation

50 Years of the Monin–Obukhov Similarity Theory

Foken

2006

599

328

This historical survey shows that Obukhov's 1946 fundamental paper on a universal length scale for exchange processes in the surface layer was the basis for the derivation of the similarity theory by Monin and Obukhov in 1954. A brief overview of the experiments and findings used to formulate the universal functions in the presently used form is given. Finally, the current status of the theory is described, covering topics such as the accuracy of the universal functions and the turbulent Prandtl number.

“…Semi-empirical functions have been established, which relate wind and temperature profiles to the surface fluxes of momentum and heat (see e.g. Nieuwstadt and Van Dop, 1982;and Garratt and Hicks, 1990). In addition, turbulence in the atmospheric surface layer can be conveniently described in terms of surface-layer similarity parameters.…”

Section: Monin-obukhov Theoryinpracticementioning

confidence: 99%

Atmospheric boundary layer research at Cabauw

Van Ulden,

Wieringa

1996

181

127

At Cabauw, The Netherlands, a 213 m high mast specifically built for meteorological research has been operational since 1973. Its site, construction, instrumentation and observation programs are reviewed. Regarding analysis of the boundary layer at Cabauw, the following subjects are discussed:terrain roughness; -Monin-Obukhov theory in practice; the structure of stable boundary layers; observed evolution of fog layers; inversion rise and early morning entrainment; use of the geostrophic wind as a predictor for wind profiles; -height variation of wind climate statistics; air pollution applications: long range transport and short range dispersion; -dependence of sound wave propagation on boundary-layer structure; testing of weather and climate models.