On trajectories of Rossby wave-packets released in a lateral shear flow

The problem of reflexion and critical level absorption of barotropic non-divergent Rossby waves in a lateral shear flow is considered with a ray tracing method. The results are compared with those of a normal mode approach. Some oceanographical applications are suggested.     

The force-free magnetosphere around an oblique rotator

The force-free magnetosphere around an obliquely rotating pulsar is studied. The basic equations reduce to two equations for two Euler potentials. One of the Euler potentials is regarded as a generalization of the stream function of the poloidal magnetic field lines in an axisymmetric rotator. Two divergence-free vectors become tangential to the surface on which this Euler potential is constant.     

Reference systems

A reference system is a relation connecting observables and their mathematical represententions. The principle of general relativity assures that any sort of coordinate system can be used to describe physical phenomena. Thus, any reference system is only a convention, There is no absolutely true reference system. Instead, people seek for a best reference system, whose meaning may differ thus need to clarify, Taking an example from Earth rotation, we discuss how to find such a best reference system. The definition of the best system will change as scientific understandings deepen and computational environments develop. Therefore, we can not stop improving reference systems. However, when replacing an existing widely-spread system, one must take great care to minimize the inconvenience caused by its transition, especially the inconvenience which users might endure. The Standards Of Fundamental Astronomy (SOFA) project being conducted by the IAU WG on Astronomical Standards has the opportunity to ease this troublesome task. The World Wide Web (WWW) will be a main device to realize the project, namely to provide working standards including reference systems to the world.     

River management system development in Asia based on Data Integration and Analysis System (DIAS) under GEOSS

This paper introduces the process of development and practical use implementation of an advanced river management system for supporting integrated water resources management practices in Asian river basins under the framework of GEOSS Asia water cycle initiative (AWCI). The system is based on integration of data from earth observation satellites and in-situ networks with other types of data, including numerical weather prediction model outputs, climate model outputs, geographical information, and socio-economic data. The system builds on the water and energy budget distributed hydrological model (WEB-DHM) that was adapted for specific conditions of studied basins, in particular snow and glacier phenomena and equipped with other functions such as dam operation optimization scheme and a set of tools for climate change impact assessment to be able to generate relevant information for policy and decision makers. In situ data were archived for 18 selected basins at the data integration and analysis system of Japan (DIAS) and demonstration projects were carried out showing potential of the new system. It included climate change impact assessment on hydrological regimes, which is presently a critical step for sound management decisions. Results of such three case studies in Pakistan, Philippines, and Vietnam are provided here.     

A note on boundary layers and wakes in rotating fluids

The flow induced by the two-dimensional line vortex moving in a rotating fluid is discussed. The governing vorticity equation is linearized adopting the Oseen approximation.First, the problem is considered on a constantf-plane. The solution shows that the Stewartson E^1/4 layer is transformed into the Oseen wake as the role of the advection becomes important.Second, the problem is considered on a-plane. When the line vortex moves westward, the solution shows a pattern of Rossby lee waves decaying downstream of the vortex and alternating flows far upstream. When the line vortex moves eastward, the inviscid solution shows definite alternating jets downstream. In a viscous case, however, the jets become less definite and identical with the above mentioned alternating flows in the far field. Far upstream, there are no disturbances because of the special propagation characteristics of Rossby waves.     

A system of astronomical constants in the relativistic framework

The relation between the units and readings of time and space coordinates of terrestrial and barycentric reference frames is discussed from the viewpoint of general relativity. Attention is paid to the unit of space coordinates since the International Astronomical Union (IAU) regulates only the unit of time in the above two frames. Two definitions of unit of length are examined and their effects on the numerical expression of coordinate transformation, equations of planetary motions, and those for light propagation time are discussed. A clear conflict is found between the IAU (1976) recommendation on the definition of the time-scales in different frames of reference and the statement that all constants in the IAU (1976) new system of astronomical constants are defined in terms of the Internationsl System of units (SI units). One of the above two definitions is proposed to resolve this conflict by the least alteration to current procedures for analysing the recent astrometric observations such as the radar/laser rangings, the range and range-rate, and the very long baseline interferometric observations. Also, an interpretation of numerical values in the IAU (1976) new system of astronomical constants is presented. It is stressed that the definition proposed in this paper requires that a formula slightly different from that in current use be employed in the numerical transformation of readings of coordinates between the terrestrial and barycentric reference frames.     

Geophysical study of the mafic belts along the margins of the japanese islands

Along the margins of the Japanese Islands there are large belts of mafic rocks that are now deeply buried. The origin of the belts is unknown: they could be either remnants of oceanic crust now trapped within the continental area, or they could be igneous bodies of continental origin. In this paper a discussion of this problem is given and new results presented.     

Interannual variability of the Guinea Dome and its possible link with the Atlantic Meridional Mode

Using a high-resolution ocean general circulation model forced by NCEP/NCAR reanalysis data, the interannual variability of the Guinea Dome is studied from a new viewpoint of its possible link with the Atlantic Meridional Mode (AMM), which is related to the meridional migration of the Intertropical Convergence Zone (ITCZ). The dome develops off Dakar seasonally from late spring to late fall owing to the wind-induced Ekman upwelling; its seasonal evolution is associated with the northward migration of the ITCZ. When the ITCZ is located anomalously northward (southward) from late spring to early summer, as a result of the wind-evaporation-sea surface temperature (SST) positive feedback with positive (negative) SST anomaly over the Northern Hemisphere, the dome becomes unusually strong (weak) in fall as a result of stronger (weaker) Ekman upwelling. This may contribute to the decay of the AMM. Thus, the coupled nature between the AMM and the Guinea Dome could be important in understanding, modeling, and predicting the tropical Atlantic variability.     

Large-scale landslides in Toyama Prefecture,central Japan,and their probable relationship with earthquakes

Large-scale landslides along the Kubusu and Besso rivers in Toyama Prefecture are developed in the Miocene Iwaine Formation, which is composed of andesitic lava, tuff, and tuff breccia. In the middle member of this formation, the tuff is easily altered to montmorillonite-bearing rock, and subsequently plays an important role in the development of landslides events, which tend to be large-scale events, as the massive lava of the upper member forms a cap rock over the tuff. The Kiritani and Koinami basins, which are flat intermontane basins located along the Kubusu and Besso rivers, respectively, are interpreted as landslide-dammed lakes, later filled with sediment. Accelerator mass spectrometry ¹⁴C ages show that the landslides forming each dam occurred simultaneously, at approximately 2500 BP. These ages were measured from wood fragments embedded in the landslide material of Kiritani, and from an in situ stump drowned during the impoundment of Koinami. If the trigger of these landslides was an earthquake, it is most likely to have been the penultimate event along the Atotsugawa fault zone.     

藏北高原D110点土壤温度的极值分析

通过藏北高原Ｄ１１０点一年中不同深度的日最高值、日最低值及日温差的分析,表明从０ｃｍ￣４０ｃｍ,土壤温度的日最高值的变化剧烈,而日最低值的变化则相对平稳,冬半年土壤温度的日最低值、日最高值比较接近,日温差较小,而且它们随时间的变化比较平稳;但夏半年（５￣９月）波动较冬半年的大,且最高温的波动要比最低温的波动大得多;随深度的增加日温差减小,在８０ｃｍ深处已基本上看不到日温差的变化。