Tidal and solar cycle effects on the OI 5577 Å, NaD and OH(8,3) airglow emissions observed at 23°S     

H. Takahashi  Y. Sahai  P.P. Batista 《Planetary and Space Science》1984,32(7):897-902

The upper mesosphere airglow emissions OI 5577, NaD and OH have been observed at Cachoeira Paulista (22.7°S; 45.0°W) Brazil. Nocturnal variations and their seasonal dependencies in amplitude and phase, and the annual variations of these emissions are presented, analysing the data obtained from 1977 to 1982 during the ascending phase of the last solar cycle. The nocturnal variations of the OI 5577 emission and the OH rotational temperature showed a significant semidiurnal oscillation, with the phase of maximum moving from midnight in January to early morning in June. Semiannual variation of the OI 5577 and NaD emissions with the maximum intensities in April/May and October/November were observed. The OH rotational temperature, however, showed an annual variation, maximum in summer and minimum in winter, while no significant seasonal variation was found in the OH emission intensities. Long-term intensity variations are also presented with the solar sunspot numbers and the 10.7 cm flux.  相似文献   

Strong and moderate nonlinear El Niño regimes     

Ken Takahashi  Boris Dewitte 《Climate Dynamics》2016,46(5-6):1627-1645

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Erratum to: Influence of South America orography on summertime precipitation in Southeastern South America     

C. Junquas  L. Li  C. S. Vera  H. Le Treut  K. Takahashi 《Climate Dynamics》2016,47(9-10):3389-3390

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Caprella watch: a new approach for monitoring butyltin residues in the ocean     

Takeuchi I  Takahashi S  Tanabe S  Miyazaki N 《Marine environmental research》2001,52(2):97-113

A comparative study on the butyltin levels in various organisms showed that marked bioaccumulation occurs in certain lower trophic levels; i.e. from seawater to phytoplankton and into caprellid amphipods, Caprella spp. Caprella spp., which inhabit algal communities and aquaculture beds in the subtidal zone, are small crustaceans with reduced movement and a life-span of less than 3 months. These characteristics indicate that Caprella spp. may be well-suited for monitoring butyltin residue changes over small spatial and temporal scales. Two groups of organisms, mussels and neogastropods, have been mainly used for monitoring butyltin in shallow water ecosystems. These invertebrates mainly inhabit the intertidal zone where the butyltin levels vary widely depending on the immersion period and exposure to the sea surface microlayer. Monitoring using neogastropods may also over estimate exposures after restrictions on tributyltin, since neogastropods show an irreversible response to residue changes owing to their long life-spans. Thus, we propose usage of Caprella spp. to monitor temporal and spatial changes in baseline concentrations of butyltins.  相似文献   

Observations of upwelling around the Izu Peninsula,Japan: May 1982     

Larry P. Atkinson  Jackson O. Blanton  Charles McClain  Thomas N. Lee  Masayuki Takahashi  Takashi Ishimaru  Joji Ishizaka 《Journal of Oceanography》1987,43(2):89-103

Hydrographic observations between the Izu Peninsula and Oshima Island, Japan, in May 1982, showed upwelling around the tip of the Peninsula and possibly also in the lee of Oshima Island. The upwelling introduced water as cold as 18 C with nitrate concentrations of 3M to the surface. Temperature/salinity analyses indicated that the upwelled water was of Kuroshio characteristics. Slightly fresher water was advected out of Sagami Bay in a coastal counter current.Contribution number 470 from the Shimoda Marine Research Center, University of Tsukuba.  相似文献   

High resolution velocity analysis of ocean bottom seismometer data by theτ-p method     

Masanao Shinohara  Naoshi Hirata  Narumi Takahashi 《Marine Geophysical Researches》1994,16(3):185-199

A method of high resolution seismic velocity analysis for ocean bottom seismometer (OBS) records is applied to the study of the shallow oceanic crust, especially sedimentary and basement layers. This method is based on the direct-p mapping and the-sum inversion. We use data obtained from a 1989 airgun-OBS experiment in the northern Yamato Basin, Japan Sea and derive P- and S-wave velocity functions that can be compared with the seismic reflection profiles. Using split-spread profile records, we obtain interface dips and true interval velocities from the OBS data. These results show good agreement with the reflection profile records, the acoustic velocities of core samples, and sonic log profiles. We also present a method for estimating errors in the derived velocity functions by calculating covariance of the derived layers' thicknesses. The estimated depth errors are about 150 m at shallow depths, which is close to the seismic wavelength used. The high resolution of this method relies on accurate determination of shot positions by GPS, spatially dense seismic observations, and the use of unsaturated reflected waves arriving after the direct water wave that are observed on low-gain component records.  相似文献   

Phytoplankton growth response to wind induced regional upwelling occurring around the Izu Islands off Japan     

Masayuki Takahashi  Michio J. Kishi 《Journal of Oceanography》1984,40(3):221-229

From frequent field observations performed in coastal waters around the Izu Islands, Japan, a clear regional upwelling associated with the wind was detected baside Niijima Island. Nutrient supply by the upwelling into the euphotic zone was confirmed, and the subsequent phytoplankton growth supported by the upwelled nutrients was evaluated. The upwelling and the nutrient supply occurred within a day over an area ofca. 400 km², and phytoplankton growth response occurred only a few days after the upwelling. Such regional upwelling is considered to be one of the major mechanisms supporting the high productivity of coastal waters.Contribution number 423 from the Shimoda Marine Research Center, University of Tsukuba.  相似文献   

Rare earth elements and Opal/CaCO<Subscript>3</Subscript> ratio of sinking particles observed with a time-series sediment trap at the mouth of Tokyo Bay     

Nobuyuki Takahashi  Shinichiro Noriki 《Journal of Oceanography》2007,63(6):941-951

A time-series sediment trap was deployed from December 1994 to February 2002 at the mouth of Tokyo Bay (35°03′ N, 139°40′ E; water depth, 850 m). Sinking particles were obtained with a time interval of one week at a depth of approximately 100 m above the sea floor. Observed total mass fluxes varied from 3.3 to 226.7 g/m²/day with an average of 28.0 g/m²/day. Concentrations of rare earth elements, Al, Ca and Si in particulate materials were measured. The combustible fraction at 450°C is assumed to be equivalent to the organic matter content. Contents of biogenic materials, namely organic matter, opal and calcium carbonate, were about 30% and the content of lithogenic material was about 70%. Using La/Yb ratios of particles from the sediment trap and Tama-gawa River and surface sediment of Tokyo Bay, it was estimated that about 50% of the lithogenic particles collected in the sediment trap at the mouth of Tokyo Bay originated from resuspended surface sediment in Tokyo Bay. An increasing trend of Opal/CaCO₃ ratio in the sinking particles was found in the spring season. It is suggested that the relative increase of diatoms is due to the decreasing dissolved inorganic nitrogen input into Tokyo Bay.  相似文献   

Diatom Assemblage and Productivity Changes during the Last 340,000 Years in the Subarctic Pacific     

Kota Katsuki  Kozo Takahashi  Makoto Okada 《Journal of Oceanography》2003,59(5):695-707

Diatoms represent the major part of the microfossils preserved in the subarctic Pacific sediments. During the warm climate intervals the diatom accumulation rate (DAR) tended to increase, whereas it tended to decrease during the cold intervals. Principal component (PC) analysis of the fossil diatom assemblages in Piston Core KH99-3 ES samples from the subarctic Pacific was carried out to investigate the paleoceanographic conditions of the area. PC1 (59.9% of the total variance) was represented by Neodenticula seminae, a characteristic species representing the high nutrient concentrations, which dominated during the interglacial periods. The DAR and PC changes can be attributed to a global origin that is influenced by the nutrient change due to intermediate water change and to a local one that is explained by the change of upwelling region. The analysis of PC2 (17.1% of the total variance) indicates the change of water mass in the western subarctic Pacific. During Marine Isotope Stages (MIS) 2 and 3, the western subarctic Pacific region was significantly influenced by the sea-ice, which may have been derived from the coastal region or a proximal marginal sea. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Preface     

Masayuki M. Takahashi  Shiro Imawaki 《Journal of Oceanography》2002,58(1):1-1

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