The impact of the Wangara experiment

Abstract

Our understanding of the structure and dynamics of the atmospheric boundary layer (ABL) is often limited by a lack of experimental data. The voluminous amount of high quality data obtained from the Wangara Experiment (Clarke et al., 1971) has contributed greatly to meeting a long-standing need, particularly for data describing the ABL in middle latitudes over land.In the surface layer the measurements provided the basis for determination of the stability dependence of the dimensionless gradients d,+, and dH arising out of Monin-Obukhov similarity theory (Hicks, 1976). In the outer layer where the choice of scaling parameters is not unique, the data have been used to determine the stability dependence of the similarity functions A, B, and C, and the most appropriate choices of scaling parameters (e.g., Yamada, 1976). In addition, the experimental data give determinations of some of the fundamental constants of turbulent flow in the ABL, such as the Von Kdrmin constant k = 0.40-0.41 (Hicks, 1969), and the neutral barotropic ABL similarity constants A,, = 1.1 and & = 4.3 (Clarke and Hess, 1974), where the subscript 0 indicates that the surface geostrophic wind was used as reference.Perhaps the greatest impact of the Wangara Experiment has been to provide a data bank which could be used to test numerical simulations of the ABL. This has been useful not only for the newly developed higher-order closure models, but also for one-layer integral models predicting the height of the mixed layer and the height of the nocturnal surface inversion layer.Lastly, the Wangara Experiment has pointed out some of the limitations and difficulties of obtaining accurate measurements of thermal winds, vertical velocity, acceleration terms, and representative spatially averaged fluxes. Microscale turbulence measurements outside the surface layer were not included in the Wangara Experiment and further experiments are needed to determine these statistics.

The diurnal evolution of <sup>222</sup>Rn and its progeny in the atmospheric boundary layer during the Wangara experiment

“…In other words, the LASDD SGS model does not require any ad-hoc specification of SGS coefficients, since they are computed dynamically based on the local dynamics of the resolved velocity and temperature fields in a self-consistent manner. The Wangara experiment was conducted during July and August 1967 at Hay in Australia (Clarke et al, 1971;Hess et al, 1981). Basu et al (2007) presented the first LES study of a diurnally varying ABL observed during the Wangara case study.…”

Micrometeorological and PBL experiments in Australia

“…In addition, recomputations of surface heat fluxes and friction velocity have been published by Hicks (1981), and discussion of the erroneous temperature differences between l-2 m and 2-4m can be found in Hicks (1976). A review of the impact of the Wangara experiment, and of the many studies in which the data have made a contribution, was presented by Hess et al (1981).…”

“…(i) Growth and structure of the daytime mixed layer, with many studies concentrating on Day 33 (e.g., see Figure 6 in Hess et al, 1981;Manins, 1982). Use of the data to test free convection arguments was made by Clarke and Hess (1973) and Wyngaard et al (1974), for example.…”

The ageostrophic method ? An update

“…Vector averages of the five simultaneous ascents are taken as one mean proflle. The site of the Wangara experiment in Southeast Australia was selected for its flatness and its uniform vegetation cover (see Clarke et al, 1971or Hess et al, 1981. The Wangara profiles were selected as test profiles in addition to the Lettau pro6le as being real profiles.…”