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S. H. Derbyshire 《Boundary-Layer Meteorology》1995,75(1-2):1-24
As argued in Part I (Derbyshire, 1995), variability is a key issue in stable boundary layers, and differences in variability between observations and idealized models may imply sytematic biases. Here we discuss how data analysis can be geared to allow for variability and thus consistency with models. Instrumental errors, smoothing methods and vertical discretization are considered. We then show how statistical averaging broadly improves the agreement of heterogeneous results in Part I with the Brost-Wyngaard closure. Recommendations are made for the information needed to analyze apparent differences between homogeneous and heterogeneous stable boundary layers.Part of UK Meteorological Office Atmospheric Processes Research Division 相似文献
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It is generally believed by those undertaking research in the fundamental aspects of geophysical fluid dynamics and meteorology that their results contribute to the improvements to numerical weather prediction and in practical weather forecasting. However, the techniques whereby the appropriate research results are selected and incorporated into the numerical models are not widely known, particularly the methods for representing the phenomena whose horizontal scale is less than that of the grid boxes.(say, 50 km). Some accounts of numerical weather prediction imply that the representation of subgrid-scale phenomena is formally similar to classical physics. In fact, atmospheric motions on these scales are not like molecular motions in an ideal gas, but show considerable structure, approximating to combinations of various idealized states. Great skill and experience in this specialized activity has been applied to deciding on these states, finding physical criteria for defining them and then modelling the relevant phenomena occurring on this scale. In this paper, we focus on a restricted range of phenomena associated with stably stratified flows, notably mountain waves, convection and clouds, and boundary layer phenomena. This category provides many examples of structures which need to be considered in detail to reconstruct the large-scale picture accurately, as well as in local forecasting. 相似文献
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The seismic refraction reversed profiling technique has been used to investigate the topography of the last interglacial soil (paleosol S1) within the central Chinese Loess Plateau near Xifeng. The results suggest an essentially flat-lying soil at a depth which varies by only a few meters over an area of more than 10 km2. In addition, the results indicate a high-velocity layer at 50-60 m depth which is thought to coincide with a layer of carbonate concretions at the base of paleosol S5. The results agree well with the local loess-paleosol stratigraphy for this area and indicate that the seismic refraction method is a rapid technique for investigating paleotopography. 相似文献
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A loess section near Lanzhou, China, has been investigated using the seismic refraction technique. The results show that the method is able to discriminate four distinct seismic boundaries within the section as well as indicating that the loess-bedrock contact occurs at a depth of more than 200 m. A 30 m deep pit was subsequently dug and revealed that the first two seismic boundaries correspond to soil units Sa (an intermediate soil within loess unit L1) and S1 (the last interglacial soil at the base of L1). These results, though preliminary, indicate the potential of the technique not only for mapping loess-bedrock contacts but also for determining the finer subsurface detail of the loess-palaeosol stratigraphy. 相似文献
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S. H. Derbyshire 《Boundary-Layer Meteorology》1999,90(2):297-325
In the stable atmospheric boundary layer (SBL), the interaction of processes in numerical weather prediction (NWP) models seems to test their representation more stringently than their separate 'validation.Some SBL schemes derived from micrometorological research seem to allow a 'decoupling behaviour when implemented in NWP. That is, turbulence dies out from the ground upwards. Such 'decoupling of the surface from atmospheric fluxes can permit dramatic and possibly unrealistic falls in surface temperature. This study traces the mechanism of model decoupling, asks whether this behaviour is in any sense correct and considers the implications.It is shown that decoupling can occur in idealized single-column models, originating from an unstable boundary-mode. This behaviour can depend critically on parameters such as surface roughness and soil thermal diffusivity as well as turbulence. But the turbulence dependence arises through the response of the boundary layer as a whole, and not just the surface-layer scheme. Such decoupling arises from the 'physics, rather than the finite-difference schemes, and appears to occur sometimes in the real atmosphere. 相似文献
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S. H. Derbyshire 《Boundary-Layer Meteorology》1999,90(3):423-446
In the light of Large Eddy Simulation and other recent work, this paper discusses methods of stable boundary-layer modelling that are established in numerical weather prediction and potentially relevant to other applications, e.g., to dispersion. It is argued that classical scaling theory is best expressed in terms of the local Richardson numbers. The theory can then be extended to treat cases where classical assumptions break down. There are indications that Richardson number models with suitable boundary conditions can mimic, at least qualitatively, some features of the very stable boundary layer. Despite advances in research modelling, detailed observational validation remains essential. 相似文献
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