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  • Author or Editor: Zbigniew Sorbjan x
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Zbigniew Sorbjan

Abstract

The parameterization of the mixed layer based on a decomposition of statistical moments into nonpenetrative and residual components and on their local similarity is discussed. The method is examined by using laboratory data for nonpenetrative convection and large-eddy simulation (LES) results for penetration convention. The examination allows discussion of various scales and similarity functions in the convective atmospheric boundary layer. Local similarity is demonstrated to be equivalent to a Level-2 closure scheme of Mellor and Yamada. The derived similarity functions are shown to agree with experimental data and with the results of numerical simulation.

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Zbigniew Sorbjan

Abstract

A parameterization method developed by Sorbjan is used to derive expressions for various statistical moments of vertical velocity, potential temperature, and humidity (or passive scalar concentration) in the convective boundary layer. The method is based on decomposing statistical moments into nonpenetrative and residual components, and their local (height-dependent) scaling. The resulting expressions are compared with atmospheric and laboratory data, and also with the results of large-eddy simulation models. An agreement between the similarity functions and the experimental data is obtained.

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Zbigniew Sorbjan

Abstract

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Zbigniew Sorbjan

Abstract

This article demonstrates that vertical profiles of the heat flux in the convective boundary layer can be diagnosed through an integration over height of the time change rates of observed potential temperature profiles. Moreover, the basic characteristics of the convective boundary layer, such as the mixed-layer height zi, the depth of the interfacial (entrainment) layer, and the beat flux zero-crossing height h 0 can be uniquely evaluated based on a time evolution of potential temperature profiles in the lower atmosphere.

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Zbigniew Sorbjan, Yuji Kodama, and Gerd Wendler

Abstract

During the austral summer of 1982/83, measurements of wind and temperature profiles were made through the atmospheric boundary layer in Adelie Land, East Antarctica, an area known for strong katabatic winds. It was found that a shallow but strong temperature inversion was developed at night, and destroyed during the day, resulting in the development of a well-mixed layer. Wind hodographs were quite regular and spiral-like at night, but irregular during the day. The mean wind direction was about 40° to the left, looking downslope, but more downslope at night and more cross-slope during the day.

The conclusion was derived that during the polar summer the flow over Antarctica is controlled by the gravitational factor (slope-induced baroclinicity), by the thermal stability (turbulent mixing), and also by the synoptic forcing.

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Wayne M. Angevine, Richard J. Doviak, and Zbigniew Sorbjan

Abstract

The vertical velocity variance in the convective atmospheric boundary layer is estimated from measurements made with a 915-MHz boundary layer wind-profiling radar. The vertical velocity variance estimates are used to infer the surface virtual heat flux through a relationship with the convective velocity scale w *. The flux estimates are compared with in situ surface flux measurements and estimates extrapolated to the surface from direct eddy correlation measurements made with a profiler and radio acoustic sounding system. The measurements were made during the Rural Oxidants in the Southern Environment II Experiment in June 1992. The experiment area is primarily pine forest, and the dominant weather conditions were hot with light winds. The profiler variance measurements are compatible with theory and earlier observations. Both remote radar methods of estimating surface virtual heat flux agree with in situ measurements to within the sampling uncertainty.

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