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481.
We used analogue modelling to investigate the factors controlling tail geometry in porphyroclast systems. Results show that: (1) σ inclusions can develop in both slipping and non-slipping modes, but δ-inclusions only form in the latter. (2) σ inclusions develop when the mantle production rate is constant and the mantle is transected by the separatrix. δ inclusions form when the mantle is initially outside the separatrix and later comes inside this line. (3) In the slipping mode, the wedge-shaped tail of σ-inclusions always has a straight external surface parallel to the shear plane, whereas in the non-slipping mode the external surface is curved inwards (external embayments). (4) Together with earlier theoretical results, σ- and δ inclusions always show stair-stepping of tails when embedded in a viscous matrix under homogeneous simple shear deformation. (5) Maximum stair-stepping occurs in the slipping mode and is at least equal to the inclusion diameter. If our models bear significant similarity to nature, then (i) the straight or curved character of σ-inclusions could mean that they had, respectively, a slipping or non-slipping interface with the surrounding recrystallized matrix, and (ii) δ-inclusions may result from shear deformation under retrogressive metamorphic conditions in thrust systems. 相似文献
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Further observational evidence of normal mode Rossby waves with higher meridional mode numbers is presented with the aid of global data from the troposphere to the stratosphere over the period November 1979 through April 1986.It is shown, without using ana priori assumption of meridional structure, that the third antisymmetric modes of zonal wavenumbers 1 and 2,i.e., (1,4) and (2,4) modes, substantially exist in the real atmosphere. These modes are, however, easily influenced by the nonuniform background field even in the equinoctial season; amplitude submaxima near the equator are apt to be dubious in the upper stratosphere so that the prototype meridional structure becomes obscure. The period of the (1,4) mode often falls into that of the (1,3) mode, about 16 days. Hence, these two modes cannot be classified simply by their periods, but the separation is made by their meridional structure.An appearance calendar of various modes is also presented for the analysis period. It is found that each mode appears irregularly throughout the year and that the year-to-year variation is fairly large. 相似文献
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A conceptual model is proposed to explain the observed aperiodicity in the short term climate fluctuations of the tropical
coupled ocean-atmosphere system. This is based on the evidence presented here that the tropical coupled ocean-atmosphere system
sustains a low frequency inter-annual mode and a host of higher frequency intra-seasonal unstable modes. At long wavelengths,
the low frequency mode is dominant while at short wavelengths, the high frequency modes are dominant resulting in the co-existence
of a long wave low frequency mode with some short wave intra-seasonal modes in the tropical coupled system. It is argued that
due to its long wavelength, the low frequency mode would behave like a linear oscillator while the higher frequency short
wave modes would be nonlinear. The conceptual model envisages that an interaction between the low frequency linear oscillator
and the high frequency nonlinear oscillations results in the observed aperiodicity of the tropical coupled system. This is
illustrated by representing the higher frequency intra-seasonal oscillations by a nonlinear low order model which is then
coupled to a linear oscillator with a periodicity of four years. The physical mechanism resulting in the aperiodicity in the
low frequency oscillations and implications of these results on the predictability of the coupled system are discussed. 相似文献
490.
A systematic and efficient method of computing normal modes for multilayered half-space 总被引:15,自引:0,他引:15
Xiaofei Chen 《Geophysical Journal International》1993,115(2):391-409