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1.
Ichiro Hasegawa 《Earth, Moon, and Planets》1996,72(1-3):311-316
Chinese and Japanese historical records of daytime fireballs, and world-wide daytime meteorite falls in the catalogue have been investigated. Among them, there are 253 and 104 records of great daytime fireballs in China and in Japan respectively, and 506 meteorite falls in the daytime are recorded in the Catalogue of Meteorites (1985). The same trends of seasonal and daily variations in the flux of daytime fireballs are clearly seen in both Chinese and Japanese records, and then the distributions of the daytime fireballs seem to suggest the association with meteorites and near-earth minor planets rather than with comets. Possible relations with minor planets, such as (1566) Icarus, (3671) Dionysius, (4450) Pan, (4486) Mithra and others are suggested. 相似文献
2.
Masayuki Takahashi Sooji Shimura Yukuya Yamaguchi Yoshihiko Fujita 《Journal of Oceanography》1971,27(2):43-50
The photo-inhibition of phytoplankton photosynthesis at higher intensities was examined with a cultured marine diatom,Phaeodactylum tricornutum, and natural samples. The question was to determine whether photo-inhibition results from excretion of photosynthetic products from cell or from an actual decrease in photosynthetic rate.
P. tricornutum cultured at 15 klux showed very little photo-inhibition up to 70 klux, and, in the sample cultured at 1 klux, most marked photo-inhibition was observed in 3 hours experiment. Extracellular release was less than 30% of particulate fixation, and did not show any extreme increase to supplement photosynthesis depression at higher light intensities. When the photosynthesis was measured during 10 minutes, both samples showed no photo-inhibition. The photosynthesis by low light sample lost the linearity of time-course with prolonged exposure at high light intensity. Observed photo-inhibition, therefore, we explained with the actual decrease in photosynthetic rate. Similar photo-inhibition could be seen in marine phytoplankton samples concentrated by filtration. 相似文献
3.
Ichiro Ishikawa Shigeaki Aoki Ryo Furue Nobuo Suginohara 《Journal of Oceanography》1996,52(5):617-632
In recognition that similarity in the density balance leads to resemblance in circulation between the two-dimensional non-rotating and three-dimensional rotating systems which have similar density stratification, we investigate convection induced by cooling at one side wall and heating at the sea surface by using a two-dimensional non-rotating model as idealized representation for the deep Pacific circulation. In the model, various vertical profiles are taken for the side wall cooling, which are assumed to correspond to the density structure of the Anatarctic Circumpolar Current. In a small diffusivity range, two important features are found to be robust against change in the vertical profile of the side wall cooling. One is that the density stratification is horizontally almost uniform. The other is that the balance in the density equation between the vertical advection and the vertical diffusion holds in the interior. Consequently, the vertical density balance, together with the equation of continuity, determines the circulation pattern for the prescribed vertical profile of the side wall cooling. The multi-layered meridional flow, which is expected to exist in the deep Pacific, is shown to form for certain vertical profiles of the side wall cooling. 相似文献
4.
5.
Photographic observations were carried out at depths of the shelf edge at the mouth of Uchiura Inlet, Suruga Bay, central Japan in order to clarify the life style of the isocrinid stalked crinoid,Metacrinus rotundus (Echinodermata). The distribution of the species was found to be restricted to a narrow area where boulders and rock outcrops were locally present. Mean density of the crinoid was 0.05 m–2, and this value was an order of magnitude smaller than that of the deeper isocrinid,Diplocrinus wyvillethomsoni, reported from the Bay of Biscay.Metacrinus rotundus formed a parabolic filtration fan with its arms recurved into the bottom current, and was thought to be a passive suspension feeder elevating the fan into the water column by its stalk. The distal half of the stalk lay along the hard substratum and about ten groups of cirri grasped the substratum. This mode of attachment was similar to that ofCenocrinus rather than that ofDiplocrinus. Metacrinus rotundus collect food at the layer between 10 and 50 cm above the sea floor, and do not utilize a higher layer even when this layer could be utilized by climbing over a larger boulder. Resuspended benthic materials are thought to be important as a food source forM. rotundus, and the crinoids seek not only locations of stronger currents but also the position where much resuspended matter is available. 相似文献
6.
Simulation of Formation and Spreading of Salinity Minimum Associated with NPIW Using a High-Resolution Model 总被引:1,自引:2,他引:1
A series of numerical experiments were conducted with a high-resolution (eddy-permitting) North Pacific model to simulate
the formation and spreading of the salinity minimum associated with the North Pacific Intermediate Water (NPIW). It was found
that two factors are required to simulate a realistic configuration of the salinity minimum: a realistic wind stress field
and small-scale disturbances. The NCEP reanalyzed wind stress data lead to better results than the Hellerman and Rosenstein
wind stress data, due to the closer location of the simulated Oyashio and Kuroshio at the western boundary. Small-scale disturbances
formed by relaxing computational diffusivity included in the advection scheme promote the large-scale isopycnal mixing between
the Oyashio and Kuroshio waters, simulating a realistic configuration of the salinity minimum. A detailed analysis of the
Oyashio water transport was carried out on the final three-year data of the experiment with reduced computational diffusivity.
Simulated transport of the Kuroshio Extension in the intermediate layer is generally smaller than the observed value, while
those of the Oyashio and the flow at the subarctic front are comparable to the observed levels. In the Oyashio-Kuroshio interfrontal
zone the zonally integrated southward transport of the Oyashio water (140–155°E) is borne by the eddy activity, though the
time-mean flow reveals the existence of a coastal Oyashio intrusion. In the eastern part (155°E–180°) the zonally integrated
transport of the Oyashio water indicates a southward peak at the southern edge of the Kuroshio Extension, which corresponds
to the branching of the recirculating flow from the Kuroshio Extension.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
7.
8.
Masayuki Takahashi Isao Koike Takashi Ishimaru Toshiro Saino Ken Furuya Yoshihiko Fujita Akihiko Hattori Shun-ei Ichimura 《Journal of Oceanography》1980,36(4):209-216
Water plumes, 20 km long or less, identified by low temperature, high salinity and high nutrient concentrations, were observed on the eastern side of Izu Islands where the Kuroshio Current or its branch flowed eastward. The T-S diagrams and the vertical profiles of oceanographic variables indicated that the water plumes resulted from the upwelling of subsurface water. A newly formed plume, characterized by a sharp temperature front and high nutrient concentrations, contained less chlorophyll than did old plumes. It is suggested that the upwelling plumes are maintained for a period long enough to allow luxuriant growth of phytoplankton. 相似文献
9.
In order to understand the actual formation process of the North Pacific Intermediate Water (NPIW), structure of subsurface intrusions of the Oyashio water and the mixing of the Oyashio and the Kuroshio waters in and around the Kuroshio Extension (KE) were examined on the basis of a synoptic CTD observation carried out in May-June 1992. The fresh Oyashio water in the south of Hokkaido was transported into KE region through the Mixed Water Region (MWR) in the form of subsurface intrusions along two main paths. The one was along the east coast of northern Japan through the First Branch of the Oyashio (FBO) and the other along the eastern face of a warm streamer which connected KE with a warm core ring through the Second Branch of the Oyashio (SBO). The fresh Oyashio water extended southward through FBO strongly mixed with the saline NPIW transported by the Kuroshio in the south of Japan (old NPIW) in and around the warm streamer. On the other hand, the one through SBO well preserved its original properties and extended eastward beyond 150°E along KE with a form of rather narrow band. The intrusion ejected Oyashio water lens with a diameter of 50–60 km southward across KE axis and split northward into the MWR involved in the interaction of KE and a warm core ring, which were supposed to be primary processes of new NPIW formation. 相似文献
10.
High parallelization efficiency in barotropic-mode computation of ocean models based on multi-grid boundary ghost area 总被引:1,自引:0,他引:1
In general, barotropic-mode computation requires the largest communication time in ocean models because of its iterative nature, when parallel computation is performed based on regional partitioning. In this study, reduction in the overhead time included in the communication in the parallel computation of the barotropic mode is considered to achieve a high parallelization efficiency of ocean models. We verify that the reduction in the communication frequency based on the multi-grid boundary ghost area reduces the total communication time. We find that this is because the sum of several kinds of overhead time for communication occupies a fairly large part of the total communication time. We discuss the trade-off between the decrease in communication time and the increase in computation time due to increased boundary area in such cases, leading to a determination of a suitable width of the multi-grid boundary that minimizes the total required time. We also discuss the efficiencies of the one- and two-dimensional partitioning of the model domain, when a multi-grid boundary is used. In general, two-dimensional partitioning is more efficient than one-dimensional for large partitioning numbers. 相似文献