Parameterization of rain cell properties using an advection-diffusion model and rain gage data     

Akira Kawamura  Kenji Jinno  Ronny Berndtsson  Takashi Furukawa 《Atmospheric Research》1996,42(1-4)

To reduce flooding risks and improve urban drainage management, there is a need to increase the forecasting accuracy for rainfall models on small typical urban time and space scales. Increased rainfall forecasting accuracy will in turn improve runoff prediction and thus, prevent flooding hazards, decrease pollution discharge through combined sewers, increase waste water treatment efficiency, etc. For this purpose, we analyzed the parameters of a two-dimensional stochastic advection-diffusion model including a Fourier domain method and an extended Kalman filter algorithm for investigation of motion, shape, size, and intensity distribution of convective rainfall. The resulting set of model parameters (advective velocity, apparent turbulent diffusion, and development/decay of rainfall rate) is used to study convective rainfall variability. It appears that the speed at which the rainfall cell is advected is not dependent on the cell development stage or apparent diffusion. Instead, there is a dependence between the source/sink term and apparent diffusion. This can be explained by the turbulent updraft of warm air which results in large rainfall intensity increase. This strong turbulence results in larger diffusion (and vice versa). The behavior of the model parameters is therefore physically explainable and relevant. The results can be used as first choice of parameter values when modeling convective rainfall over ungaged areas.  相似文献   

Management and application of Geotechnical Data: The Geotechnical Data Information System of the Tokyo Metropolitan Government     

Motomu Ishii  Kenji Ishimura  Toshio Nakayama 《Environmental Geology》1992,19(3):169-178

In the Tokyo metropolis many geological surveys are carried out in conjunction with building construction work and urban base improvement undertakings. Furthermore, the Institute of Civil Engineering (ICE) of the Tokyo Metropolitan Government (TMG) has been conducting surveys on urban geology, land subsidence, and geodetics. Thus, ICE of TMG keeps a lot of geological data. In order to plan for a more effective use of these data, the Geotechnical Data Information System of Tokyo Metropolitan Government was organized in 1985, and since 1986, it has become fully implemented.This Geotechnical Data Information System has incorporated a relational data base into a mainframe computer, the NEC ACOS System 430, and as of March 1989 it can retrieve and graphically present borehole, deep-well, and groundwater data.The authors wish to introduce in this article the organizational structure of the Geotechnical Data Information System of TMG, a summary of the data base system, standards of input data, and applicable examples of the data base.  相似文献   

The July 1998 Papua New Guinea Earthquake: Mechanism and Quantification of Unusual Tsunami Generation     

Kenji Satake  Yuichiro Tanioka 《Pure and Applied Geophysics》2003,160(10-11):2087-2118

— The unusual tsunami generated by the July 17, 1998 Papua New Guinea earthquake was investigated on the basis of various geophysical observations, including seismological data, tsunami waveform records, and on-land and submarine surveys. The tsunami source models were constructed for seismological high-angle and low-angle faults, splay fault, and submarine slumps. Far-field and near-field tsunamis computed from these models were compared with the recorded waveforms in and around Japan and the measured heights along the coast around Sissano Lagoon, respectively. In order to reproduce the far-field tsunami waveforms, small sources such as splay fault or submarine slump alone were not enough, and a seismological fault model was required. Relocated aftershock distribution and observed coastal subsidence were preferable for the low-angle fault, but the low-angle fault alone could not reproduce the large near-field tsunamis. The low-angle fault with additional source, possibly a submarine slump, is the most likely source of the 1998 tsunami, although other possibilities cannot be excluded. Computations from different source models showed that the far-field tsunami amplitudes are proportional to the displaced water volume at the source, and the comparison with the observed tsunami amplitudes indicated that the displaced water volume at the 1998 tsunami source was ～0.6 km³. The near-filed tsunami heights, on the other hand, are determined by the potential energy of displaced water, and the comparison with the observed heights showed that the potential energy was ～2 × 10¹² J.  相似文献   

Response to the comment by R. Stalder on “composition of aqueous fluid coexisting with mantle minerals at high pressure and its bearing on the differentiation of the earth’s mantle”     

Kenji Mibe  Toshitsugu Fujii 《Geochimica et cosmochimica acta》2004,68(4):929-930

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Evidence and Implications of Recent Climate Change in Northern Alaska and Other Arctic Regions   总被引：19，自引：0，他引：19  

Larry D. Hinzman  Neil D. Bettez  W. Robert Bolton  F. Stuart Chapin  Mark B. Dyurgerov  Chris L. Fastie  Brad Griffith  Robert D. Hollister  Allen Hope  Henry P. Huntington  Anne M. Jensen  Gensuo J. Jia  Torre Jorgenson  Douglas L. Kane  David R. Klein  Gary Kofinas  Amanda H. Lynch  Andrea H. Lloyd  A. David McGuire  Frederick E. Nelson  Walter C. Oechel  Thomas E. Osterkamp  Charles H. Racine  Vladimir E. Romanovsky  Robert S. Stone  Douglas A. Stow  Matthew Sturm  Craig E. Tweedie  George L. Vourlitis  Marilyn D. Walker  Donald A. Walker  Patrick J. Webber  Jeffrey M. Welker  Kevin S. Winker  Kenji Yoshikawa 《Climatic change》2005,72(3):251-298

The Arctic climate is changing. Permafrost is warming, hydrological processes are changing and biological and social systems are also evolving in response to these changing conditions. Knowing how the structure and function of arctic terrestrial ecosystems are responding to recent and persistent climate change is paramount to understanding the future state of the Earth system and how humans will need to adapt. Our holistic review presents a broad array of evidence that illustrates convincingly; the Arctic is undergoing a system-wide response to an altered climatic state. New extreme and seasonal surface climatic conditions are being experienced, a range of biophysical states and processes influenced by the threshold and phase change of freezing point are being altered, hydrological and biogeochemical cycles are shifting, and more regularly human sub-systems are being affected. Importantly, the patterns, magnitude and mechanisms of change have sometimes been unpredictable or difficult to isolate due to compounding factors. In almost every discipline represented, we show how the biocomplexity of the Arctic system has highlighted and challenged a paucity of integrated scientific knowledge, the lack of sustained observational and experimental time series, and the technical and logistic constraints of researching the Arctic environment. This study supports ongoing efforts to strengthen the interdisciplinarity of arctic system science and improve the coupling of large scale experimental manipulation with sustained time series observations by incorporating and integrating novel technologies, remote sensing and modeling.  相似文献   

3-D Modelling of Plate Interfaces and Numerical Simulation of Long-term Crustal Deformation in and around Japan     

Chihiro Hashimoto  Kenji Fukui  Mitsuhiro Matsu’ura 《Pure and Applied Geophysics》2004,161(9-10):2053-2068

— We developed a 3-D simulation model for long-term crustal deformation due to steady plate subduction in and around Japan by incorporating viscoelastic slip-response functions into a realistic 3-D plate interface model, constructed on the basis of the topography of ocean floors and hypocenter distributions of earthquakes. The lithosphere-asthenosphere system is modelled by an elastic surface layer overlying a Maxwellian viscoelastic half-space. Kinematic interaction at plate interfaces is rationally represented by the increase of tangential displacement discontinuity (fault slip) across the interfaces. With this model, giving the steady slip rates at plate interfaces calculated from NUVEL-1A, we simulated long-term crustal deformation due to steady plate subduction in and around Japan. The simulated crustal deformation pattern is characterized by steep uplift at island arcs, sharp subsidence at ocean trenches and gentle uplift at outer rises. The numerical results show the strong dependence of the deformation pattern on the 3-D geometry of plate interfaces.  相似文献   

Variation in noble gas isotopic composition of gas samples from the Aegean arc, Greece     

Aya Shimizu  Hirochika Sumino  Keisuke Nagao  Kenji Notsu  Panagiotis Mitropoulos 《Journal of Volcanology and Geothermal Research》2005,140(4):118-339

In contrast to most other arcs with oceanic plate subduction, the Aegean arc is characterized by continent–continent subduction. Noble gas abundances and isotopic compositions of 45 gas samples have been determined from 6 volcanoes along the arc, 2 islands in the back-arc region and 7 sites in the surrounding areas. The ³He/⁴He ratios of the samples ranged from 0.027R_A to 6.2R_A (R_A denotes the atmospheric ³He/⁴He ratio of 1.4×10⁻⁶), demonstrating that even the maximum ³He/⁴He ratio in the region is significantly lower than the maximum ratios of most oceanic subduction systems, which are equal to the MORB value of 8±1 R_A. Regional variations in the ³He/⁴He ratio were observed both along and across the arc. The maximum ³He/⁴He ratio was obtained from Nisyros volcano located in the eastern end of the arc, and the ratio decreased westward possibly reflecting the difference in potential degree of crustal assimilation or the present magmatic activity in each volcano. Across the volcanic arc, the ³He/⁴He ratio decreased with an increasing distance from the arc front, reaching a low ratio of 0.063R_A in Macedonia, which suggested a major contribution of radiogenic helium derived from the continental crust. At Nisyros, a temporal increase in ³He/⁴He ratio due to ascending subsurface magma was observed after the seismic crisis of 1995–1998 and mantle neon was possibly detected. The maximum ³He/⁴He ratio (6.2R_A) in the Aegean region, which is significantly lower than the MORB value, is not probably due to crustal assimilation at shallow depth or addition of slab-derived helium to MORB-like mantle wedge, but inherent characteristics of the subcontinental lithospheric mantle (SCLM) beneath the Aegean arc.  相似文献   

Modeling the seismic source and tsunami generation of the December 12, 1992 Flores Island,Indonesia, earthquake   总被引：3，自引：0，他引：3  

Dannie Hidayat  Jeffrey S. Barker  Kenji Satake 《Pure and Applied Geophysics》1995,144(3-4):537-554

On December 12, 1992 a large earthquake (M _s 7.5) occurred just north of Flores Island, Indonesia which, along with the tsunami it generated, killed more than 2,000 people. In this study, teleseismicP andSH waves, as well asPP waves from distances up to 123°, are inverted for the orientations and time histories of multiple point sources. By repeating the inversion for reasonable values of depth, time separation and spatial separation, a 2-fault model is developed. Next, the vertical deformation of the seafloor is estimated from this fault model. Using a detailed bathymetric model, linear and nonlinear tsunami propagation models are tested. The data consist of a single tide gauge record at Palopo (650 km to the north), as well as tsunami runup height measurements from Flores Island and nearby islands. Assuming a tsunami runup amplification factor of two, the two-fault model explains the tide gauge record and the tsunami runup heights on most of Flores Island. It cannot, however, explain the large tsunami runup heights observed near Leworahang (on Hading Bay) and Riangkroko (on the northeast peninsula). Massive coastal slumping was observed at both of these locations. A final model, which in addition to the two faults, includes point sources of large vertical displacement at these two locations explains the observations quite well.  相似文献   

Introduction to “tsunamis: 1992–94”     

Kenji Satake  Fumihiko Imamura 《Pure and Applied Geophysics》1995,144(3-4):373-379

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Analysis of seismological and tsunami data from the 1993 Guam earthquake     

Yuichiro Tanioka  Kenji Satake  Larry Ruff 《Pure and Applied Geophysics》1995,144(3-4):823-837

The fault parameters of the Guam earthquake of August 8, 1993 are estimated from seismological analyses, and the possibility of identifying the actual fault plane from tsunami waveforms is tested. The Centroid Moment Tensor solution of long-period surface waves shows one nodal plane shallowly dipping to the north and the other nodal plane steeply dipping to the south. The seismic moment is 3.5×10²⁰ Nm and the corresponding moment magnitude is 7.7. The Moment Tensor Rate Function inversion ofP waves also yields a similar focal mechanism and seismic moment. The point source depth is estimated as 40–50 km.This earthquake generated tsunamis that propagated toward the Japanese coast along the Izu-Bonin-Mariana ridge system. The tsunamis are recorded on ocean bottom pressure gauges and tide gauges. Numerical computation of tsunamis shows that the computed waveforms from the two possible fault planes match well with the observed tsunami waveforms. The numerical computation also shows that the tsunami waveforms at Guam Island, just above the fault, should contain useful information regarding the identification of the actual fault plane. However, the current sampling rate of the tide gauges is so small that the records cannot help the identification.  相似文献