Origin of extreme summers in Europe: the Indo-Pacific connection     

Swadhin Behera  Jayanthi V. Ratnam  Yukio Masumoto  Toshio Yamagata 《Climate Dynamics》2013,41(3-4):663-676

Extreme summers of Europe are usually affected by blocking highs that shift between Western and Eastern Europe to cause regional variations in the surface temperature anomalies. Generally, the blocking high induces a regional temperature dipole with poles of warm and cold anomalies on two sides of Europe. The extreme summers of Western Europe, when the Eastern Europe is colder than normal, are usually associated with the teleconnections arising from positive Indian Ocean Dipole (IOD) events. In contrast, analogous warm events in Eastern Europe are usually associated with La Niña. The western Pacific conditions that prevail during the turnaround phase of El Niño to La Niña are found to be responsible for developing the extreme Eastern Europe events. The role of North Atlantic Oscillation (NAO) is not blatant for the Eastern Europe summers though it has a weaker influence on Western Europe summers for which IOD plays a dominant role: The seasonal July–August correlation for Western Europe temperature with IOD index is higher than that with the NAO index. The teleconnections for both types of extremes are associated with a Rossby wavetrain that travel around the globe to reach the Europe. This circumglobal teleconnection is largely determined by the location of the tropospheric heat source. For Western Europe warm events, major contributions come from the atmospheric convections/diabatic heating over northwest India and southern Pakistan. For the Eastern Europe events, the convections over northwest Pacific, south of Japan, are found to project the signals on to the mid-latitude wave-guide. These patterns of teleconnection are so robust that those can be seen on daily to seasonal time-scales of atmospheric anomalies. The wavetrains are found to set-in a couple of weeks prior to the development of blocking highs and extreme hot conditions over Europe.  相似文献   

The design of diamond Compton telescope     

Kinya Hibino  Toshisuke Kashiwagi  Shoji Okuno  Kaori Yajima  Yukio Uchihori  Hisashi Kitamura  Takeshi Takashima  Mamoru Yokota  Kenji Yoshida 《Astrophysics and Space Science》2007,309(1-4):541-544

We have developed radiation detectors using the new synthetic diamonds. The diamond detector has an advantage for observations of “low/medium” energy gamma rays as a Compton telescope. The primary advantage of the diamond detector can reduce the photoelectric effect in the low energy range, which is background noise for tracking of the Compton recoil electron. A concept of the Diamond Compton Telescope (DCT) consists of position sensitive layers of diamond-striped detector and calorimeter layer of CdTe detector. The key part of the DCT is diamond-striped detectors with a higher positional resolution and a wider energy range from 10 keV to 10 MeV. However, the diamond-striped detector is under development. We describe the performance of prototype diamond detector and the design of a possible DCT evaluated by Monte Carlo simulations.   相似文献   

Testing of the bandpass eddy covariance method for a long-term measurement of water vapour flux over a forest     

Tsutomu Watanabe  Katsumi Yamanoi  Yukio Yasuda 《Boundary-Layer Meteorology》2000,96(3):473-491

The bandpass eddy covariance method has been used to measure the turbulent flux of scalar quantities using a slow-responsescalar sensor. The method issimilar in principle to the traditional eddy correlation method but includes the estimation of high-frequency components of the flux on the basis of cospectral similarity in the atmospheric surface layer. In order to investigate the performance of the method, measurements of the water vapour flux over a forest with the bandpass eddy covariance method and the direct eddy correlation method were compared. The flux obtained by the bandpass eddy covariance method agreed with that by the eddy correlation method within ±20% for most cases, in spite of a rather slow sensor-response of the adopted hygrometer. This result supports its relevance to a long-term continuous operation, since a stable, low-maintenance,general-purpose sensor canbe utilized for scalar quantities. Oneweak point of the method isits difficulty in principle to measure the correct flux when the magnitude of the sensible heat flux is very small, because the method uses the sensible heat flux as a standard reference for the prediction of undetectable high-frequency components of the scalar flux. An advanced method is then presented to increase its robustness. In the new method, output signals from a slow-response sensor are corrected using empirical frequency-responsefunctions for the sensor,thereby extending the width of the bandpass frequency region where components of the flux are directly measured (not predicted). The advanced method produced correct fluxes for all cases including the cases of small sensible heat flux. The advanced bandpass eddy covariance method is thus appropriate for along-term measurement of the scalar fluxes.  相似文献   

Mass distribution of Antarctic ordinary chondrites and the estimation of the fall-to-specimen ratios     

Yukio Ikeda  Makoto Kimura 《Meteoritics & planetary science》1992,27(4):435-441

Abstract— The cumulative mass distributions (mass range > 100 g) of each type of Japanese and U.S. Antarctic ordinary chondrites are compared with those of non-Antarctic falls and those obtained from the present-day flux of meteorites. The steeper slope of the mass distribution of Antarctic chondrites is indicative of the presence of several chondrite showers. The fall-to-specimen ratio of Antarctic ordinary chondrites larger than 100 g is about 1:2, indicating that half of them are shower components. The fall-to-specimen ratios of each group range from 1:1 to 1:6; those of the Japanese and U.S. Antarctic meteorite collections are 1:1 to 1:2 and 1:4 for H chondrites, 1:1 to 1:2 and 1:2 for L chondrites, and 1:2 and 1:6 for LL chondrites, indicating that the Japanese collection includes less abundant shower components than the U.S. collection. The fall-to-specimen ratios of each H4-6 and L4-6 type range from 1:1 to 1:4, and U.S. H6 and Japanese H4 have the low ratios of 1:4.  相似文献   

Petrology and mineralogy of the Yamato-86751 CV3 chondrite     

Toshio Murakami  Yukio Ikeda 《Meteoritics & planetary science》1994,29(3):397-409

Abstract— The Y-86751 chondrite (CV3) consists of fine-grained Ca- and Al-rich inclusions (CAIs), amoeboid olivine inclusions (AOIs), spinel-rich inclusions, chondrules with and without dark rims, dark inclusions, isolated minerals, metal-sulfide aggregates, and matrix. Olivines in chondrules without dark rims and AOIs coexist with magnetite and show strong zoning from a magnesian core to a ferroan rim. Spinels in spinel-rich inclusions show similar zoning. This zoning seems to be caused by exchange reaction of olivine and spinel with an oxidized nebular gas prior to the accretion onto the parent body, and the Mg/Fe diffusion in olivines and spinels took place at a temperature of about 830–860 K. At the same time, enstatite in chondrules without dark rims was replaced by ferroan olivine at the grain boundaries. This feature suggests that chondrules without dark rims, fine-grained CAIs, spinel-rich inclusions, and AOIs have experienced oxidation in an oxidizing nebular gas. The oxygen fugacity of the oxidized nebular gas was >10^?27.3 bars at about 830 K, being more than 10⁴x larger than that of the canonical nebular gas. Magnetite occurs in the Y-86751 matrix in close association with Ni-rich taenite and Co-rich metal, and it was produced under a condition with the oxygen fugacity of ～10^?38 bars at a temperature of about 620–650 K. On the other hand, olivines in chondrules with dark rims and dark inclusions are magnesian and rich in MnO. They do not show such strong zoning. Probably they were in equilibrium with a nebular gas under a redox condition different from the oxidized nebular gas that produced the zoned olivines in chondrules without dark rims.  相似文献   

Impact of the equatorial Atlantic sea surface temperature on the tropical Pacific in a CGCM   总被引：1，自引：0，他引：1  

Wataru Sasaki  Takeshi Doi  Kelvin J. Richards  Yukio Masumoto 《Climate Dynamics》2014,43(9-10):2539-2552

Many coupled general circulation models (CGCMs) suffer from serious model bias in the zonal gradient of sea surface temperature (SST) in the equatorial Atlantic. The bias of the equatorial Atlantic SST (EASST) may affect the interannual variability of the equatorial Atlantic, which in turn may influence the state of the tropical Pacific. In this paper we investigate the impact of the bias and the interannual variability of the EASST on the tropical Pacific in a CGCM. To determine the impact of the interannual variability of the EASST on the tropical Pacific, we compare a run in a fully coupled mode (CTL run) and a run in which the EASST is nudged toward the climatological monthly mean of the SST in the CTL run, but full air-sea coupling is allowed elsewhere (AT_m run). We find that, when the interannual variability of the EASST is excluded, the thermocline depth in the eastern equatorial Pacific is deepened, and the amplitude of the El Niño/Southern Oscillation is reduced by 30 % compared to the CTL run. The impact of the bias of the EASST on the tropical Pacific is investigated by comparing the AT_m run and a run in which the EASST is nudged toward the observed climatological monthly mean SST (AT_o run). It is found that, when the bias of the EASST is removed (i.e. AT_o run), the Gill–Matsuno type response to the warm SST anomalies in the western equatorial Atlantic induces low-level cyclonic anomalies in the eastern South Pacific, which leads to a deeper thermocline and colder SST in the South Pacific as compared to AT_m. The colder SST in the South Pacific reduces the precipitation along the South Pacific convergence zone. Our results of the model experiments demonstrate the importance of the EASST to the tropical Pacific climate.  相似文献   

Analysis of surface changes using primitive events     

Yukio Sadahiro 《International journal of geographical information science》2013,27(6):523-538

This paper develops a method for analysing changes in a surface, a scalar function defined over a two-dimensional region. The method is based on the topological method for static surfaces that uses critical points (peaks, bottoms, and cols) and their connecting lines. To extend the topological method to spatiotemporal domain, four types of primitive events are proposed: (1) generation, (2) disappearance, (3) movement, and (4) switch. The change of a surface is described by a combination of these primitives. From surfaces of two times a set of primitive events that cause the change is deduced. They are stored in GIS as spatial objects with attributes, and their spatio-temporal pattern is visually analysed. To test the validity of the method, the change of a retail cluster in Shinjuku and Shibuya area in Tokyo is analysed. The empirical study yielded some interesting findings that help us understand changes in the spatial structure of retailing.  相似文献   

Analysis of the spatial relations among point distributions on a discrete space     

Yukio Sadahiro 《International journal of geographical information science》2013,27(7):997-1014

This paper proposes a method of analyzing spatial relations among point distributions on a discrete space. Spatial topology and proximity are discussed in an integrated framework at both local and global scales. Local relations are described by geographical representations, whereas global relations are visualized by graph representations. The latter also provide a means of classifying the point distributions. The proposed method is applied to school location planning in Japan. The results reveal the appealing properties of the method and provide empirical findings.  相似文献   

A major change in magma sources in late Mesozoic active margin of the circum-Sea of Japan domain: Geochemical constraints from late Paleozoic to Paleogene mafic dykes in the Sergeevka belt,southern Primorye,Russia     

Victor P. Nechaev  Evgene V. Sklyarov  Yukio Isozaki  Nikolay N. Kruk  Alexey V. Travin  Yukiyasu Tsutsumi  Eugenia V. Nechaeva 《Island Arc》2021,30(1):e12426

More than 30 mafic dykes crop out in the Sergeevka belt in the coastal South Primorye, Far East Russia, of which geologic settings have been unclear for years. This study conducted major- and trace elements characterization, Sr–Nd isotope analyses, and Ar–Ar amphibole and U–Pb zircon datings for these rocks in order to identify their origin. The results demonstrated that all dykes are characterized by high Ba/Yb and low Nb/Y, Zr/Y, and Th/Yb ratios, which suggest their origin from arc melts derived from thin wedge mantle and shallow-dipping slab. These dykes are clearly separated into two distinct age/geochemistry suites; that is, the Paleogene and Early Cretaceous one with dolerites/basalts and adakitic rocks, and the Permian–Triassic one with high-Mg and high-Al gabbro-dolerite varieties. Their geochemistry suggests that the older suite was sourced from a primitive depleted MORB mantle (DMM)-type mantle, whereas the younger suite from an enriched mantle II (EM2)-type mantle domain. The transition in source type from DMM to EM2 occurred during the Jurassic-earliest Cretaceous time, probably by a strong influence of a mantle plume onto the long-continuing subduction-related magmatism. The plume influence reached the maximum when the unique meimechite-picrite complex formed in the region.  相似文献   

Motion of Mars: 1935–1976     

Yukio Niimi 《Celestial Mechanics and Dynamical Astronomy》1982,26(2):179-179

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