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J. A. Businger

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J. A. Businger

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With Prandtl's theory of the mixing length as the point of beginning, a theory concerning the structure of the atmospheric surface layer is proposed on similar assumptions as were put forward by Lettau. The novel feature in the present treatment lies in the fact that the acceleration due to the frictional part of the turbulence is considered to be dependent on stability, whereas Lettau assumed a constant value for this acceleration. Although this theory is not exact, it may promote a better understanding of atmospheric turbulence.

A dimensionless stability number is introduced; it enables one to obtain a simple survey of all states of the atmospheric surface layer. The theory is tested with observations of Rider (1954). The requirements for a further experimental program are established.

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J. A. Businger

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J. A. Businger

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A concept for the mixing length in diabatic conditions is introduced and elaborated. The basic idea is that convective energy has effect on the mixing length but not on the size of the largest eddies. The theory developed on this concept of the mixing length for the diabatic wind profile gives satisfactory agreement with observations over a wide stability range.

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J. A. Businger

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Corrections to the sensible heat flux due to fluctuations in the specific humidity recently proposed by Brook (1978) have been shown to be incorrect by Frank and Emmitt (1981). However, it is easy to misinterpret Frank and Emmitt’s paper. Here an effort is made to clarify the issue and to sketch what its importance is to the energy balance of the hydrological cycle. By expanding the specific enthalpy flux into the fluxes of sensible heat and latent heat, it is found that a good first-order approximation shows that no corrections are necessary, which is in agreement with Frank and Emmitt's result.

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J. M. Wilczak and J. A. Businger

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J. W. Deardorff and J. A. Businger

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J. A. Businger and J. W. Deardorff

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J. A. Businger and P. M. Kuhn

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Simultaneous night observations with four different sensors for the long-wave atmospheric radiation were obtained with a radiosonde, specially equipped for this purpose. The sensors consisted of (1) a radiometersonde as developed by Sumoi and Kuhn, (2) a disc-type total radiometer, and (3) two spherical total radiometers (i.e., a ‘black ball’ as developed by Gergen and a blackened silver sphere).

The total radiations measured by the disc and the radiometersonde are in fairly good agreement. The total radiations measured with the two spheres showed a difference which may partly be caused by convection and conduction inside the ‘black ball’. The total radiation measured with the spherical sensors tends to be less than that of the disc in the upper part of the sounding which may be caused by the transparency of the atmosphere at those heights. The temperature difference between the air temperature and the radiative equilibrium temperature seems to be more or less related to the divergence of the net radiation.

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J. M. Wilczak and Joost A. Businger

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The energetics of the dry convective boundary layer is studied by partitioning the turbulent heat flux into thermally indirect (w′θ′<0) and thermally direct (w′θ′>0) components as a function of z/Zi. It is found that except for the inversion transition region, the thermally direct and indirect fluxes each have linear profiles. The integrated profiles indicate that a fraction A of the buoyant production of thermal kinetic energy is available to do the work of entrainment, where A is the boundary layer entrainment coefficient. A simple mixing analysis shows that this would require the integrated production of energy due to surface heating to be independent of the entrainment process. Sub-partitioning the thermally indirect flux into two components (w′<, θ′>0 and w′>0, θ′<0) reveals that an upward flux of cold air is the dominant thermally indirect term throughout the bulk of the mixed layer. Further, in the inversion transition layer the measured negative mean entrainment beat flux (w′θ′)i is principally due to a net upward flux of locally colder air, and not to a net downward flux of locally warmer air. These results are interpreted in terms of a highly idealized dome-wisp model of the entrainment mechanism.

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