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Fedorov V. M. Frolov D. M. Velasco Herrera V. M. N. Soon W. W.-H. Cionco R. G. 《Izvestiya Atmospheric and Oceanic Physics》2021,57(10):1239-1253
Izvestiya, Atmospheric and Oceanic Physics - On the basis of calculations of insolation and insolation characteristics, taking into account changes in solar activity, the causes of global climatic... 相似文献
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Ronald M. Cionco 《Boundary-Layer Meteorology》1978,15(1):81-93
Canopy wind profiles can often be represented by an exponential function such that wind-speeds in these vegetative canopies are a function of height and the attenuation coefficient of this wind profile relationship. To be more precise, canopy flow is a function of canopy density, element flexibility, and height. An index of canopy flow, therefore, can be defined as a conservative measure of the gross flow response to the presence of various types of roughness elements. For this study, windspeed profile data of two quite different canopy density experiments — field and wind tunnel - have been analyzed based on least-square fittings. The results indicate that the two sets of index values of canopy flow behave in a similar manner with maxima occurring for optimum densities of one-third the potential full array of roughness elements. These index values also differ by some 0.2, but are still compatible when one accounts for the respective levels of turbulence within these dissimilar canopies. 相似文献
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Y. S. Wang D. R. Miller D. E. Anderson R. M. Cionco J. D. Lin 《Boundary-Layer Meteorology》1992,59(1-2):125-139
Turbulent flow within and above an almond orchard was measured with three-dimensional wind sensors and fine-wire thermocouple sensors arranged in a horizontal array. The data showed organized turbulent structures as indicated by coherent asymmetric ramp patterns in the time series traces across the sensor array. Space-time correlation analysis indicated that velocity and temperature fluctuations were significantly correlated over a transverse distance more than 4m. Integral length scales of velocity and temperature fluctuations were substantially greater in unstable conditions than those in stable conditions. The coherence spectral analysis indicated that Davenport's geometric similarity hypothesis was satisfied in the lower frequency region. From the geometric similarity hypothesis, the spatial extents of large ramp structures were also estimated with the coherence functions. 相似文献
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Ronald M. Cionco 《Boundary-Layer Meteorology》1972,2(4):453-465
From a large group of both simple and complex canopies, the following properties have been identified. (1) For simple canopies (rice paddy, wheat field, larch tree plantation, and wind-tunnel wooden pegs), the intensity of turbulence was constant with height and decreased slowly above the vegetation. (2) For forests, wind-tunnel model trees and immature corn plants, the intensity of turbulence had a maximum in the main crown layer, a minimum in the trunk space and decreased gradually above the vegetation. (3) Seasonal variations of the turbulence intensities occurred in deciduous vegetation where the turbulence levels increased from the bare branch case to the leafy crown case. (4) In regard to thermal stability, the intensity of turbulence increased as the stability ratio decreased in a forest canopy. (5) Passage of larger-scale eddies and disturbances over or through the roughness elements produced high intensity levels both immediately above and below the canopy-air interface. (6) The intensity of turbulence increased as the density and structural complexity of the vegetation increased. 相似文献
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We have performed N -body numerical simulations of the exchange of angular momentum between a massive planet and a 3D Keplerian disc of planetesimals. Our interest is directed at the study of the classical analytical expressions of the lineal theory of density waves, as representative of the dynamical friction in discs 'dominated by the planet' and the orbital migration of the planets with regard to this effect. By means of a numerical integration of the equations of motion, we have carried out a set of numerical experiments with a large number of particles ( N ≥10 000) , and planets with the mass of Jupiter, Saturn and one core mass of the giant planets in the Solar system ( M c =10 M⊕ ) . The torque, measured in a phase in which a 'steady forcing' is clearly measurable, yields inward migration in a minimum-mass solar disc (Σ∼10 g cm-2 ), with a characteristic drift time of ∼ a few 106 yr. The planets predate the disc, but the orbital decay rate is not sufficient to allow accretion in a time-scale relevant to the formation of giant planets. We found reductions of the measured torque on the planet, with respect to the linear theory, by a factor of 0.38 for M c , 0.04 for Saturn and 0.01 for Jupiter, due to the increase in the perturbation on the disc. The behaviour of planets whose mass is larger than M c is similar to the one of type II migrators in gaseous discs. Our results suggest that, in a minimum mass, solar planetesimals disc, type I migrations occur for masses smaller than M c , whereas for this mass value it could be a transition zone between the two types of migration. 相似文献
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A wind-profile index for canopy flow 总被引：5，自引：0，他引：5
Ronald M. Cionco 《Boundary-Layer Meteorology》1972,3(2):255-263
Canopy wind profiles can often be represented by an exponential function. The associated attenuation index,a, is found to be proportional to [(Flexibility)(Leaf Area)(Density)]1/3. Leastsquare values of the index have been calculated for wind profiles in about a dozen natural and artificial canopies which included oats, wheat, corn, rice, sunflowers, larch trees, citrus trees, Xmas trees, plastic strips, wooden pegs and bushel baskets. It is found that canopy flow is a function of canopy density, element flexibility, and height and that the behaviour of artificial canopy elements is compatible with that of natural vegetation. The same calculations also show that the attenuation coefficient: (a) is not a universal constant, (b) is however, rather limited in range (-0.3 to 3.0), (c) varies with stage of growth, and (d) increases as density and flexibility increase. A compilation ofa-values for several canopies reveals that lowa-values correspond to sparsely arrayed rigid elements while higha-values correspond to densely arrayed and flexible elements. Finally, lowa-values appear to be relatively independent of wind speed, while higha-values tend to increase as wind speeds increase. 相似文献
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Ronald M. Cionco 《Boundary-Layer Meteorology》1983,26(4):325-335
A canopy flow coupling parameter is defined from earlier canopy flow research to describe the degree of coupling of air flow in vegetation to ambient flow of the surface boundary layer. This ratio concept employs an exponential wind-height relationship in the canopy referenced to the logarithmic wind-height relationship of the ambient air in close proximity to the vegetation interface. Qualitatively, the coupling ratio decreases as the index of canopy flow increases. Numerical criteria are derived to quantify the coupling upwind of the canopy, at the leading edge, through the transition zone, through the zone of established flow, at the trailing edge, and downwind from the canopy domain. It was found that coupling was relatively independent of element density for the more dense arrays, but increased rapidly as densities became more sparsely arrayed. A high degree of coupling existed both upwind and downwind of well-defined domains, while a degeneration of coupling is clearly evident through the zone of established flow. A seasonal contrast in coupling was also discerned. Gravity and slope flows contributed to a higher degree of coupling. 相似文献
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