A New Method for Polar Field Interpolation   总被引：1，自引：0，他引：1  

X. Sun  Y. Liu  J. T. Hoeksema  K. Hayashi  X. Zhao 《Solar physics》2011,270(1):9-22

The photospheric magnetic field in the Sun’s polar region is not well observed compared to the low-latitude regions. Data are periodically missing due to the Sun’s tilt angle, and the noise level is high due to the projection effect on the line-of-sight (LOS) measurement. However, the large-scale characteristics of the polar magnetic field data are known to be important for global modeling. This report describes a new method for interpolating the photospheric field in polar regions that has been tested on MDI synoptic maps (1996 – 2009). This technique, based on a two-dimensional spatial/temporal interpolation and a simple version of the flux transport model, uses a multi-year series of well-observed, smoothed north (south) pole observations from each September (March) to interpolate for missing pixels at any time of interest. It is refined by using a spatial smoothing scheme to seamlessly incorporate this filled-in data into the original observation starting from lower latitudes. For recent observations, an extrapolated polar field correction is required. Scaling the average flux density from the prior observations of slightly lower latitudes is found to be a good proxy of the future polar field. This new method has several advantages over some existing methods. It is demonstrated to improve the results of global models such as the Wang–Sheeley–Arge (WSA) model and MHD simulation, especially during the sunspot minimum phase.  相似文献   

Evaluation of global warming impacts for different levels of stabilization as a step toward determination of the long-term stabilization target     

Ayami Hayashi  Keigo Akimoto  Fuminori Sano  Shunsuke Mori  Toshimasa Tomoda 《Climatic change》2010,98(1-2):87-112

In order to estimate the benefit attributable to alleviating global warming for a kind of cost–benefit analysis of global warming mitigation, global warming impacts were quantitatively evaluated for a pathway of unmitigated CO₂ emissions and three pathways to stabilize the atmospheric CO₂ concentration at different levels, keeping unchanged the assumed conditions on population and GDP growths, although the GDP losses which will be caused due to the warming mitigation for the three stabilization pathways are taken into account. The evaluation results show that global warming will reduce the world total number of deaths caused by thermal stress owing to the large decrease in the cold-related deaths; it will increase the water stress in some regions, while it will decrease the stress in other regions; reductions in CO₂ emissions will decrease the probability of THC collapse and terrestrial biodiversity loss; and it will enhance an increase in the wheat production potential.  相似文献   

Effects of CO<Subscript>2</Subscript> on Marine Fish: Larvae and Adults     

Atsushi Ishimatsu  Takashi Kikkawa  Masahiro Hayashi  Kyoung-Seon Lee  Jun Kita 《Journal of Oceanography》2004,60(4):731-741

CO₂-enriched seawater was far more toxic to eggs and larvae of a marine fish, silver seabream, Pagrus major, than HCl-acidified seawater when tested at the same seawater pH. Data on the effects of acidified seawater can therefore not be used to estimate the toxicity of CO₂, as has been done in earlier studies. Ontogenetic changes in CO₂ tolerance of two marine bony fishes (Pag. major and Japanese sillago, Sillago japonica) showed a similar, characteristic pattern: the cleavage and juvenile stages were most susceptible, whereas the preflexion and flexion stages were much more tolerant to CO₂. Adult Japanese amberjack, Seriola quinqueradiata, and bastard halibut, Paralichthys olivaceus, died within 8 and 48 h, respectively, during exposure to seawater equilibrated with 5% CO₂. Only 20% of a cartilaginous fish, starspotted smooth-hound, Mustelus manazo, died at 7% CO₂ within 72 h. Arterial pH initially decreased but completely recovered within 1-24 h for Ser. quinqueradiata and Par. olivaceus at 1 and 3% CO₂, but the recovery was slower and complete only at 1% for M. manazo. During exposure to 5% CO₂, Par. olivaceus died after arterial pH had been completely restored. Exposure to 5% CO₂ rapidly depressed the cardiac output of Ser. quinqueradiata, while 1% CO₂ had no effect. Both levels of ambient CO₂ had no effect on blood O₂ levels. We tentatively conclude that cardiac failure is important in the mechanisms by which CO₂ kills fish. High CO₂ levels near injection points during CO₂ ocean sequestration are likely to have acute deleterious effects on both larvae and adults of marine fishes. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Splitting of the subtropical gyre in the western North Pacific     

Keiichi Hasunuma  Kozo Yoshida 《Journal of Oceanography》1978,34(4):160-172

Examined here is a hypothetical idea of the splitting of the subtropical gyre in the western North Pacific on the basis of two independent sources of data,i.e., the long-term mean geopotential-anomaly data compiled by the Japanese Oceanographic Data Center and the synoptic hydrographic (STD) data taken by the Hakuho Maru in the source region of the Kuroshio and the Subtropical Countercurrent in the period February and March 1974. Both of the synoptic and the long-term mean dynamic-topographic maps reveal three major ridges, which indicate that the western subtropical gyre is split into three subgyres. Each subgyre is made up of the pair of currents, the Kuroshio and the Kuroshio Countercurrent, the Subtropical Countercurrent and a westward flow lying just south of the Countercurrent (18°N–21°N), and the northern part of the North Fquatorial Current and an eastward flow at around 18°N. The subgyres are more or less composed of a train of anticyclonic eddies with meridional scales of between 300 and 600 km, so that the volume transport of the subgyres varies by a factor of two or more from section to section. The upper-water characteristics also support the splitting of the subtropical gyre; the water characteristics are fairly uniform within each subgyre, but markedly different between them. The northern rim of each subgyre appears as a sharp density front accompanied by an eastward flow. The bifurcations of the sharp density fronts across the western boundary current indicate that the major part of the surface waters in the North Equatorial Countercurrent is not brought into the Kuroshio. The western boundary current appears as a continuous feature of high speed, but the waters transported change discontinuously at some places.  相似文献   

Spatial Heterogeneity in Distributions of Chlorophyll a Derivatives in the Subarctic North Pacific during Summer   总被引：1，自引：1，他引：1  

Masato Hayashi  Ken Furuya  Hiroshi Hattori 《Journal of Oceanography》2001,57(3):323-331

The distribution of chlorophyll a derivatives was examined in samples collected from the subarctic North Pacific during July to September 1997. Pheophorbide a, pheophytin a and pyropheophorbide a as determined by high performance liquid chromatography (HPLC) were the major derivatives recorded. The distribution patterns of chlorophyll a and its derivatives showed a strong vertical and horizontal heterogeneity. Patches with high concentration of derivatives seemed to be associated with high concentration of chlorophyll a. A clear east-west gradient was observed in both chlorophyll a and pheophorbide a integrated from the surface to 100 m depth with significantly higher amounts of both the pigments in the Western Subarctic Gyre and in the Bering Sea than in the Alaskan Gyre. In contrast, no apparent gradient was observed in the integrated pyropheophorbide a and pheophytin a. Grazing experiments conducted with the copepod (Neocalanus cristatus) and salp (Cyclosalpa bakeri) fed on five species of phytoplankton cultures, showed a marked difference in the composition of the derivatives in their fecal pellets. Pyropheophorbide a was dominant in the copepod fecal pellet regardless of the phytoplankton species fed on. In the salp, however, pheophytin a and pheophorbide a were found in the fecal pellets, the relative concentrations varying with the algal food. Spatial heterogeneity in the distribution of the derivatives is considered to reflect local variations in dominant herbivorous processes.  相似文献   

Millimeter polarimetry of star-forming regions: magnetic field structure around low-mass stars     

M. Tamura  S. Hayashi  J. H. Hough 《Astrophysics and Space Science》1995,224(1-2):21-24

We have measured polarization of the 1.1 mm and 0.8 mm continuum emission for 3 pre-T Tauri stars and 2 T Tauri stars. Positive detections were made for NGC 1333 IRAS 4 and IRAS 16293-2422, while L1551 IRS 5 and HL Tau were only marginally detected. For GG Tau we measured a 2 upper limit of 3%. The polarization is interpreted in terms of thermal emission by magnetically aligned dust grains in circumstellar disks or envelopes. We have found a definite geometrical relation between the polarization and other circumstellar structure.  相似文献   

Rainfall on the Meghalaya plateau in northeastern India—one of the rainiest places in the world     

Fumie Murata  Taiichi Hayashi  Jun Matsumoto  Haruhisa Asada 《Natural Hazards》2007,42(2):391-399

Monthly and daily variations in rainfall over Cherapunjee and Mawsynram on the Meghalaya plateau of northeastern India are analysed. Cherapunjee and Mawsynram are well known as two of the places with the heaviest rainfall in the world. The daily rainfall variation is attributed to the influence of synoptic scale disturbances, with a periodicity of 10–20 days, and the orographic interaction. The annual and monthly highest rainfalls over Cherapunjee during the 31 years from 1973 to 2003 were much larger than mean values.  相似文献   

Active, weak and break spells in the Indian summer monsoon     

V. S. Prasad  T. Hayashi 《Meteorology and Atmospheric Physics》2007,95(1-2):53-61

Summary Active weak and break phases of the Indian summer monsoon for the period 1958–2002 are studied using ERA-40 data. The criteria for identifying the break are proposed and tested using the 850 hPa level horizontal wind shear. Independent datasets such as All-India Rainfall, NOAA Outgoing Long-wave Radiation and CMAP rainfall datasets are used for the verification of the proposed criteria. On leave from the National Center for Medium Range Weather Forecasting, A-50 Institutional Area, Phase-II, Sector 62, Noida, U.P., India.  相似文献   

Late Cenozoic volcanic activity in the Chugoku area, southwest Japan arc during back-arc basin opening and reinitiation of subduction   总被引：3，自引：0，他引：3  

Jun-Ichi Kimura  Tomoyuki Kunikiyo  Isaku Osaka  Takashi Nagao  Seiki Yamauchi  Susumu Kakubuchi  Shomei Okada  Norie Fujibayashi  Ryuhei Okada  Hisashi Murakami  Takashi Kusano  Koji Umeda  Shintaro Hayashi  Tsuneari Ishimaru  Atusi Ninomiya  Atsushi Tanase 《Island Arc》2003,12(1):22-45

Abstract Temporal–spatial variations in Late Cenozoic volcanic activity in the Chugoku area, southwest Japan, have been examined based on 108 newly obtained K–Ar ages. Lava samples were collected from eight Quaternary volcanic provinces (Daisen, Hiruzen, Yokota, Daikonjima, Sambe, Ooe–Takayama, Abu and Oki) and a Tertiary volcanic cluster (Kibi Province) to cover almost all geological units in the province. Including published age data, a total of 442 Cenozoic radiometric ages are now available. Across‐arc volcanic activity in an area approximately 500 km long and 150 km wide can be examined over 26 million years. The period corresponds to syn‐ and post‐back‐arc basin opening stages of the island arc. Volcanic activity began in the central part of the rear‐arc ca 26 Ma. This was followed by arc‐wide expansion at 20 Ma by eruption at two rear‐arc centers located at the eastern and western ends. Expansion to the fore‐arc occurred between 20 and 12 Ma. This Tertiary volcanic arc was maintained until 4 Ma with predominant alkali basalt centers. The foremost‐arc zone activity ceased at 4 Ma, followed by quiescence over the whole arc between 4 and 3 Ma. Volcanic activity resumed at 3 Ma, covering the entire rear‐arc area, and continued until the present to form a Quaternary volcanic arc. Adakitic dacite first occurred at 1.7 Ma in the middle of the arc, and spread out in the center part of the Quaternary volcanic arc. Alkali basalt activities ceased in the area where adakite volcanism occurred. Fore‐arc expansion of the volcanic arc could be related to the upwelling and expansion of the asthenosphere, which caused opening of the Japan Sea. Narrowing of the volcanic zone could have been caused by progressive Philippine Sea Plate subduction. Deeper penetration could have caused melting of the slab and resulted in adakites. Volcanic history in the Late Cenozoic was probably controlled by the history of evolution of the upper mantle structure, coinciding with back‐arc basin opening and subsequent reinitiation of subduction.  相似文献   

Sulphide minerals in early Archean chemical sedimentary rocks of the eastern Pilbara district, Western Australia     

S. Kojima  T. Hanamuro  K. Hayashi  M. Haruna  H. Ohmoto 《Mineralogy and Petrology》1998,64(1-4):219-235

Summary The occurrence and paragenesis of sulphide minerals in chemical sedimentary rocks from the McPhee and the Towers Formations of the Warrawoona Group, eastern Pilbara Craton were examined, in order to evaluate the Archean sedimentary environment. The chemical sedimentary facies of both formations are comprised of chert or chertcarbonate units, which are highly depleted in detrital materials. The cherty rocks are mostly composed of microcrystalline quartz, containing significant types of syndepositional (or diagenetic) sulphide minerals. In particular, the cherty rocks in the Towers Formation (North Pole Chert, Marble Bar Chert) include primary sulphide minerals, such as pyrite, chalcopyrite, sphalerite, monoclinic pyrrhotite, pentlandite, gersdorffite and millerite. This assemblage and the measured FeS content (8.4–10.4 mol%) of sphalerite associated with the Fe-sulphide minerals suggest that the cherty rocks were formed under reducing conditions at temperatures below 200°C (about 150°C), and also that the metamorphic temperature of the rocks was less than 325 °C. Furthermore, the virtual absence of detrital materials and the minor element compositions imply that the cherty rocks of the eastern Pilbara Block were formed by rapid precipitation from reducing hydrothermal solutions.

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Sulfide in chemischen sedimentgesteinen des älteren Archaikums im östlichen Pilbara block, Westaustralien

Zusammenfassung Das Auftreten und die Paragenese von Sulfiden in chemischen Sedimentgesteinen der McPhee und der Towers Formation der Warrawoona Gruppe, östlicher Pilbara Block, wurden untersucht, um das sedimentäre Milieu im Archaikum besser abschätzen zu können. Die chemisch-sedimentäre Fazies beider Formationen besteht aus Chert- oder Chert-Karbonat-Einheiten, die hochgradig an detritärem Material verarmt sind. Die Cherts bestehen aus mikrokristallinem Quartz, der beträchtliche Mengen an syngenetischen bzw. syndiagenetischen Sulfiden enthält. Vor allem die Cherts der Towers Formation (North Pole Chert, Marble Bar Chert) führen Pyrit, Kupferkies, Zinkblende, monoklinen Magnetkies, Pentlandit, Gersdorffit und Millerit als primäre Sulfide. Diese Vergesellschaftung und die gemessenen FeS-Gehalte der mit den Fe-Sulfiden assoziierten Zinkblende (8.4–10.4 Mol%), weisen darauf hin, daß die Cherts unter reduzierenden Bedingungen bei Temperaturen unter 200°C entstanden sind und daß die Matamorphosetemperatur 325 °C nicht überschritten hat. Das Fehlen detritärer Sedimentkomponenten und die Spurenelementzusammensetzungen lassen darauf schließen, daß die Cherts im östlichen Pilbara Block durch rasche Ausfällung aus reduzierenden hydrothermalen Lösungen entstanden sind.

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