Japanese early-warning for debris flows and slope failures using rainfall indices with Radial Basis Function Network   总被引：3，自引：1，他引：2  

Nobutomo Osanai  Takeshi Shimizu  Kazumasa Kuramoto  Shinichi Kojima  Tomoyuki Noro 《Landslides》2010,7(3):325-338

Early-warning systems for natural disasters are important tools for disaster risk reduction and for achieving sustainable development and livelihoods. In 2005, the Japanese government initiated a new nationwide early-warning system for landslides disasters. The main methodology of the system is to set a criterion for occurrences of debris flows and slope failures based on several rainfall indices (60-min cumulative rainfall and soil–water index) in each 5-km grid mesh covering all of Japan. Because many of the records of mass movements are lacking in scientific precision on timing and location, the system applies Radial Basis Function Network methods to set the criterion based primarily on rainfall data recorded as not triggering disasters. Since the end of March 2007, under torrential rainfall conditions, early-warning information has been disseminated as part of weather news using TV, radio, and the Internet. Because of the increasing worldwide recognition of the importance of early-warning systems for natural disaster reduction, the aim of this article is to introduce the new Japanese early-warning system to the international landslide community. In this article, the method, the system, and the result of its application to landslide disasters in 2009 are presented.  相似文献   

High-resolution observations of dissolved isoprene in surface seawater in the Southern Ocean during austral summer 2010–2011     

Sohiko Kameyama  Satoshi Yoshida  Hiroshi Tanimoto  Satoshi Inomata  Koji Suzuki  Hisayuki Yoshikawa-Inoue 《Journal of Oceanography》2014,70(3):225-239

We measured dissolved isoprene (2-methyl-1,3-butadiene; C₅H₈) concentrations in a broad area of the southern Indian Ocean and in the Indian sector of the Southern Ocean from 35°S to 64°S and from 37°E to 111°E during austral summer 2010–2011. Isoprene concentrations were continuously measured by use of a proton-transfer-reaction mass spectrometer combined with a bubbling-type equilibrator. Concentrations of isoprene and its emission flux throughout the study period ranged from 0.2 to 395 pmol L^?1 and from 181 to 313 nmol m^?2 day^?1, respectively, the averages being generally higher than those of previous studies. Although we found a significant linear positive relationship between isoprene and chlorophyll-a concentrations (r ² = 0.37, n = 36, P < 0.001), the correlation coefficient was lower than previously reported. In contrast, in the high-latitude area (>53°S) we identified a significant negative correlation (r ² = 0.59, n = 1263, P < 0.001) between isoprene and the temperature-normalized partial pressure of carbon dioxide (n-pCO₂), used as an indicator of net community production in this study. This suggests that residence times and factors controlling variations in isoprene and n-pCO₂ are similar within a physically stable water column.  相似文献   

Impacts of Indian Ocean SST biases on the Indian Monsoon: as simulated in a global coupled model     

Chloé Prodhomme  Pascal Terray  Sébastien Masson  Takeshi Izumo  Tomoki Tozuka  Toshio Yamagata 《Climate Dynamics》2014,42(1-2):271-290

In this study, the impact of the ocean–atmosphere coupling on the atmospheric mean state over the Indian Ocean and the Indian Summer Monsoon (ISM) is examined in the framework of the SINTEX-F2 coupled model through forced and coupled control simulations and several sensitivity coupled experiments. During boreal winter and spring, most of the Indian Ocean biases are common in forced and coupled simulations, suggesting that the errors originate from the atmospheric model, especially a dry islands bias in the Maritime Continent. During boreal summer, the air-sea coupling decreases the ISM rainfall over South India and the monsoon strength to realistic amplitude, but at the expense of important degradations of the rainfall and Sea Surface Temperature (SST) mean states in the Indian Ocean. Strong SST biases of opposite sign are observed over the western (WIO) and eastern (EIO) tropical Indian Ocean. Rainfall amounts over the ocean (land) are systematically higher (lower) in the northern hemisphere and the south equatorial Indian Ocean rainfall band is missing in the control coupled simulation. During boreal fall, positive dipole-like errors emerge in the mean state of the coupled model, with warm and wet (cold and dry) biases in the WIO (EIO), suggesting again a significant impact of the SST errors. The exact contributions and the distinct roles of these SST errors in the seasonal mean atmospheric state of the coupled model have been further assessed with two sensitivity coupled experiments, in which the SST biases are replaced by observed climatology either in the WIO (warm bias) or EIO (cold bias). The correction of the WIO warm bias leads to a global decrease of rainfall in the monsoon region, which confirms that the WIO is an important source of moisture for the ISM. On the other hand, the correction of the EIO cold bias leads to a global improvement of precipitation and circulation mean state during summer and fall. Nevertheless, all these improvements due to SST corrections seem drastically limited by the atmosphere intrinsic biases, including prominently the unimodal oceanic position of the ITCZ (Inter Tropical Convergence Zone) during summer and the enhanced westward wind stress along the equator during fall.  相似文献   

Primary melt from Sannome-gata volcano,NE Japan arc: constraints on generation conditions of rear-arc magmas     

Takeshi?KuritaniEmail author  Takeyoshi?Yoshida  Jun-Ichi?Kimura  Toshiro?Takahashi  Yuka?Hirahara  Takashi?Miyazaki  Ryoko?Senda  Qing?Chang  Yoshinori?Ito 《Contributions to Mineralogy and Petrology》2014,167(2):969

The conditions under which rear-arc magmas are generated were estimated using primary basalts from the Sannome-gata volcano, located in the rear of the NE Japan arc. Scoriae from the volcano occur with abundant crustal and mantle xenoliths, suggesting that the magma ascended rapidly from the upper mantle. The scoriae show significant variations in their whole-rock compositions (7.9–11.1 wt% MgO). High-MgO scoriae (MgO > ~9.5 wt%) have mostly homogeneous ⁸⁷Sr/⁸⁶Sr ratios (0.70318–0.70320), whereas low-MgO scoriae (MgO < ~9 wt%) have higher ⁸⁷Sr/⁸⁶Sr ratios (>0.70327); ratios tend to increase with decreasing MgO content. The high-MgO scoriae are aphyric, containing ~5 vol% olivine microphenocrysts with Mg# [100 × Mg/(Mg + Fe²⁺)] of up to 90. In contrast, the low-MgO scoriae have crustal xenocrysts of plagioclase, alkali feldspar, and quartz, and the mineralogic modes correlate negatively with whole-rock MgO content. On the basis of these observations, it is inferred that the high-MgO scoriae represent primary or near-primary melts, while the low-MgO scoriae underwent considerable interaction with the crust. Using thermodynamic analysis of the observed petrological features of the high-MgO scoriae, the eruption temperature of the magmas was constrained to 1,160–1,220 °C. Given that the source mantle was depleted MORB-source mantle, the primary magma was plausibly generated by ~7 % melting of a garnet-bearing spinel peridotite; taking this into consideration, and considering the constraints of multi-component thermodynamics, we estimated that the primary Sannome-gata magma was generated in the source mantle with 0.5–0.6 wt% H₂O at 1,220–1,230 °C and at ~1.8 GPa, and that the H₂O content of the primary magma was 6–7 wt%. The rear-arc Sannome-gata magma was generated by a lower degree of melting of the mantle at greater depths and lower temperatures than the frontal-arc magma from the Iwate volcano, which was also estimated to be generated by ~15 % melting of the source mantle with 0.6–0.7 wt% H₂O at ~1,250 °C and at ~1.3 GPa.  相似文献   

Tree-ring reconstructed summer temperature anomalies for temperate East Asia since 800 C.E.     

Edward R. Cook  Paul J. Krusic  Kevin J. Anchukaitis  Brendan M. Buckley  Takeshi Nakatsuka  Masaki Sano 《Climate Dynamics》2013,41(11-12):2957-2972

We develop a summer temperature reconstruction for temperate East Asia based on a network of annual tree-ring chronologies covering the period 800–1989 C.E. The East Asia reconstruction is the regional average of 585 individual grid point summer temperature reconstructions produced using an ensemble version of point-by-point regression. Statistical calibration and validation tests indicate that the regional average possesses sufficient overall skill to allow it to be used to study the causes of temperature variability and change over the region. The reconstruction suggests a moderately warm early medieval epoch (ca. 850–1050 C.E.), followed by generally cooler ‘Little Ice Age’ conditions (ca. 1350–1880 C.E.) and 20th century warming up to the present time. Since 1990, average temperature has exceeded past warm epochs of comparable duration, but it is not statistically unprecedented. Superposed epoch analysis reveals a volcanic forcing signal in the East Asia summer temperature reconstruction, resulting in pulses of cooler summer conditions that may persist for several years. Substantial uncertainties remain, however, particularly at lower frequencies, thus requiring caution and scientific prudence in the interpretation of this record.  相似文献   

Hydrometeorological behaviour of pine and larch forests in eastern Siberia     

Shuko Hamada  Takeshi Ohta  Tetsuya Hiyama  Takashi Kuwada  Atsuhiro Takahashi  Trofim C. Maximov 《水文研究》2004,18(1):23-39

Seasonal changes in the water and energy exchanges over a pine forest in eastern Siberia were investigated and compared with published data from a nearby larch forest. Continuous observations (April to August 2000) were made of the eddy‐correlation sensible heat flux and latent heat flux above the canopy. The energy balance was almost closed, although the sum of the turbulent fluxes sometimes exceeded the available energy flux (R_n ? G) when the latent heat flux was large; this was related to the wind direction. We examined the seasonal variation in energy balance components at this site. The seasonal variation and magnitude of the sensible heat flux (H) was similar to that of the latent heat flux (λE), with maximum values occurring in mid‐June. Consequently, the Bowen ratio was around 1·0 on many days during the study period. On some clear days just after rainfall, λE was very large and the sum of H and λE exceeded R_n ? G. The evapotranspiration rate above the dry canopy from May to August was 2·2 mm day^?1. The contributions of understory evapotranspiration (E_u) and overstory transpiration (E_o) to the evapotranspiration of the entire ecosystem (E_t) were both from 25 to 50% throughout the period analysed. These results suggest that E_u plays a very important role in the water cycle at this site. From snowmelt through the tree growth season (23 April to 19 August 2000), the total incoming water, comprised of the sum of precipitation and the water equivalent of the snow at the beginning of the melt season, was 228 mm. Total evapotranspiration from the forest, including interception loss and evaporation from the soil when the canopy was wet, was 208–254 mm. The difference between the incoming and outgoing amounts in the water balance was from +20 to ?26 mm. The water and energy exchanges of the pine and larch forest differed in that λE and H increased slowly in the pine forest, whereas λE increased rapidly in the larch forest and H decreased sharply after the melting season. Consequently, the shape of the Bowen ratio curves at the two sites differed over the period analysed, as a result of the differences in the species in each forest and in soil thawing. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   

An excess motion of the ascending node of mercury in the observations used by Le Verrier     

Takeshi Inoue 《Celestial Mechanics and Dynamical Astronomy》1993,56(1-2):69-69

  相似文献   

Static Spheroidal Deformation of Degree 1 - Consistency Relation, Stress Solution and Partials     

Shuhei Okubo  Takeshi Endo 《Geophysical Journal International》1986,86(1):91-102

This paper treats the static spheroidal deformation of degree 1 in detail. We give a physical interpretation of the consistency relation imposed on it. the relation serves as a guiding principle to find out all of its members. Following Okubo & Saito, we derive the partial derivatives of the degree 1 Love numbers with respect to density, bulk modulus and rigidity.  相似文献   

Melt inclusion analysis of the Unzen 1991–1995 dacite: implications for crystallization processes of dacite magma     

Koshi Nishimura  Tatsuhiko Kawamoto  Tetsuo Kobayashi  Takeshi Sugimoto  Shigeru Yamashita 《Bulletin of Volcanology》2005,67(7):648-662

Dacitic magma, a mixture of high-temperature (T) aphyric magma and low-T crystal-rich magma, was erupted during the 1991–1995 Mount Unzen eruptive cycle. Here, the crystallization processes of the low-T magma were examined on the basis of melt inclusion analysis and phase relationships. Variation in water content of the melt inclusions (5.1–7.2 wt% H₂O) reflected the degassing history of the low-T magma ascending from deeper levels (250 MPa) to a shallow magma chamber (140 MPa). The ascent rate of the low-T magma decreased markedly towards the emplacement level as crystal content increased. Cooling of magma as well as degassing-induced undercooling drove crystallization. With the decreasing ascent rate, degassing-induced undercooling decreased in importance, and cooling became more instrumental in crystallization, causing local and rapid crystallization along the margin of the magma body. Some crystals contain scores of melt inclusions, whereas there are some crystals without any inclusions. This heterogeneous distribution suggests the variation in the crystallization rate within the magma body; it also suggests that cooling was dominant cause for melt entrapment. Numerical calculations of the cooling magma body suggest that cooling caused rapid crystal growth and enhanced melt entrapment once the magma became a crystal-rich mush with evolved interstitial melt. The rhyolitic composition of melt inclusions is consistent with this model.Editorial responsibility: H Shinohara  相似文献   

Dynamical rupture process on a three-dimensional fault with non-uniform frictions and near-field seismic waves   总被引：1，自引：0，他引：1  

Takeshi Mikumo  Takashi Miyatake 《Geophysical Journal International》1978,54(2):417-438

Summary. Dynamical rupture process on the fault is investigated in a quasi-three-dimensional faulting model with non-uniform distributions of static frictions or the fracture strength under a finite shearing pre-stress. The displacement and stress time functions on the fault are obtained by solving numerically the equations of motion with a finite stress—fracture criterion, using the finite difference method.
If static frictions are homogeneous or weakly non-uniform, the rupture propagates nearly elliptically with a velocity close to that of P waves along the direction of pre-stress and with a nearly S wave velocity in the direction perpendicular to it. The rise time of the source function and the final displacements are larger around the centre of the fault. In the case when the static frictions are heavily non-uniform and depend on the location, the rupture propagation becomes quite irregular with appreciably decreased velocities, indicating remarkable stick-slip phenomena. In some cases, there remain unruptured regions where fault slip does not take place, and high stresses remain concentrated up to the final stage. These regions could be the source of aftershocks at a next stage.
The stick—slip faulting and irregular rupture propagation radiate high-frequency seismic waves, and the near-field spectral amplitudes tend to show an inversely linear frequency dependence over high frequencies for heavily non-uniform frictional faults.  相似文献