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91.
Based on the baroclinic semi-geostrophic model,the effects of zonally symmetrical Ekman-CISK mechanism on the characteristics of 30—60-day low frequency oscillation(LFO)near theequator are investigated.It is found that the theoretical results are in good agreement with theobservational features of LFO.Besides,the planetary-scale LFO with the period of 30—60 d couldbe triggered by the Ekman-CISK mechanism,and the growth rate of perturbation with wavenumber 1 is in order of O (10~(-6)s~(-1)).The zonal propagation of LFO and the correspondinglongitudinal-height structure of physical quantities are also discussed in detail. 相似文献
92.
根据全球高分辨率的海洋环流模式 (POCM)的数值模拟结果 ,发现北赤道流区上层海洋流的季节内变化是以准 60天振荡为主 ,该准 60天振荡的振幅有年际变化。利用 2 .5层海洋模式 ,确定了NEC区纬向Rossby波解的频散关系。该关系表明 :北赤道流区行星波和波长小于 5 70km的Rossby波都为稳定波 ;波长小于 2 0 0 0km ,大于 5 70km的Rossby为不稳定波 ;最不稳定波的相速度和波长分别为 - 0 .1 45m·s- 1 和 785km。斜压不稳定是北赤道流区上层海洋准 60天振荡的主要形成机制 相似文献
93.
根据1500~1997年地震资料分析研究,江苏-南黄海地区M≥5中强地震具有显著的干支60年周期性特征。作者对其独特的预测功能进行了初步研究。结果表明,未来几年该区依然存在5~6级地震的危险性,该区本世纪第二地震活跃幕可能持续到2009~2012年前后。 相似文献
94.
A statistical investigation of the location of onset of intermediate and gyrating ion populations in the Earth60r771u35213610/xxlarge8217.gif" alt="rsquo" align="BASELINE" BORDER="0">s foreshock is presented based on Fixed Voltage Analyzer data from ISEE 1. This study reveals the existence of a spatial boundary for intermediate and gyrating ion populations that coincides with the reported ULF wave boundary. This boundary position in the Earth60r771u35213610/xxlarge8217.gif" alt="rsquo" align="BASELINE" BORDER="0">s foreshock depends strongly upon the magnetic cone angle 60r771u35213610/xxlarge952.gif" alt="theta" align="BASELINE" BORDER="0">BX and appears well defined for relatively large cone angles, though not for small cone angles. As reported in a previous study of the ULF wave boundary, the position of the intermediate-gyrating ion boundary is not compatible with a fixed growth rate of the waves resulting from the interaction between a uniform beam and the ambient plasma. The present work examines the momentum associated with protons which travel along this boundary, and we show that the variation of the boundary position (or equivalently, the associated particle momentum) with the cone angle is related to classical acceleration mechanisms at the bow shock surface. The same functional behavior as a function of the cone angle is obtained for the momentum predicted by an acceleration model and for the particle momentum associated with the boundary. However, the model predicts systematically larger values of the momentum than the observation related values by a constant amount; we suggest that this difference may be due to some momentum exchange between the incident solar-wind population and the backstreaming particles through a wave-particle interaction resulting from a beam plasma instability. 相似文献
95.
ZONALLY SYMMETRICAL EKMAN-CISK MECHANISM AND 30—60-DAY LOW FREQUENCY OSCILLATION NEAR THE EQUATOR*
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Based on the baroclinic semi-geostrophic model,the effects of zonally symmetrical Ekman-CISK mechanism on the characteristics of 30—60-day low frequency oscillation(LFO)near the equator are investigated.It is found that the theoretical results are in good agreement with the observational features of LFO.Besides,the planetary-scale LFO with the period of 30—60 d could be triggered by the Ekman-CISK mechanism,and the growth rate of perturbation with wave number 1 is in order of O (10-6s-1).The zonal propagation of LFO and the correspondinglong itudinal-height structure of physical quantities are also discussed in detail. 相似文献
96.
The 30–60 day oscillation is an important aspect of the atmospheric variance in the tropical area. A number of works have
been done on this phenomenon, this article is a further one. A quasi-geostrophic linear model that consists of a two-layer
free atmosphere and a well-mixed boundary layer is used to investigate the instability of intraseasonal oscillation, its propagation
and vertical structures. Results show that the dynamical coupling and interaction between the barotropic and baroclinic components
via boundary layer convergence / divergence are responsible for the appearance of a new kind of low-frequency wave. Such wave
is very different from the traditional tropical Rossby wave. It can propagate westward and eastward. Some behaviours of it
appear to resemble the observed 30–60 day oscillation mode in many aspects, such.as vertical structures, zonal and meridional
propagations. Now many researchers emphasize the direct relationship between CISK-Kelvin mode and the tropical atmospheric
30–60 oscillation. It is considered that CISK-Rossby mode should not be neglected. 相似文献
97.
Osmotic stress represents a limiting physical parameter for marine organisms and especially for sessile scleractinian corals which are known to be basically stenohaline and osmoconformers. The salinity changes may cause important cellular damage since corals lack any developed physiological regulatory system. One mechanism of reaction to deleterious conditions is the rapid increase of the induction of heat shock proteins. This study highlights the modulation of the expression of a mitochondrial heat shock protein, such as the chaperonin Hsp60, in the animal tissues of the scleractinian coral Seriatopora caliendrum under three salinity scenarios (hypersalinity of 45 ppt, hyposalinity of 25 ppt and extreme hyposalinity of 15 ppt). The study was performed during the time course of a 2-day period and accompanied also by the assessment of the coral health condition. For each salinity stress S. caliendrum responds differently at the morphological and cellular levels, since the Hsp60 exhibited specific patterns of expression and the coral showed different tissue appearance. Furthermore, the response reflects the severity and exposure length of the disturbance. However, the results indicate that S. caliendrum seems able to tolerates high salinity better than low salinity. In particular, in extreme hyposalinity conditions, a considerable gradual down-regulation of Hsp60 was detected accompanied by necrosis and degradation of the coral tissues. The study suggests that Hsp60 may be involved in the mechanisms of cellular response to stress caused by exposure to adverse salinity. 相似文献