The anoxic water mass in Hiuchi-Nada     

Hidetaka Takeoka  Tadashi Ochi  Kazuhiko Takatani 《Journal of Oceanography》1986,42(1):1-11

Distribution of the anoxic water mass in the eastern part of Hiuchi-Nada was investigated from 1981 to 1983. A cold water mass was found on the bottom of the area concerned in summer, and a second (i.e. lower) thermocline appeared just above the cold water mass. The anoxic water was observed below a second thermocline. The horizontal distribution of the cold water mass coincided with that of the anoxic water mass, and also with a region of high concentration of organic matter in the sediment. These results suggest two important effects of the second thermocline on the generation of the anoxic water mass. Firstly, it prevents supply of dissolved oxygen from the upper to bottom layer of the water column. Secondly, it accelerates settling of particulate material resulting in a large accumulation of organic matter in the bottom water and the sediment which leads to an increase in the rate of oxygen consumption. The net oxygen consumption rate in the bottom layer in this sea was much smaller than that in Mikawa Bay where anoxia occurs at almost the same level as in Hiuchi-Nada. This finding also suggests the important role of the second thermocline.  相似文献   

Association of picophytoplankton distribution with ENSO events in the equatorial Pacific between 145°E and 160°W     

Kazuhiko Matsumoto  Ken Furuya  Takeshi Kawano 《Deep Sea Research Part I: Oceanographic Research Papers》2004,51(12):1319

Climatological variability of picophytoplankton populations that consisted of >64% of total chlorophyll a concentrations was investigated in the equatorial Pacific. Flow cytometric analysis was conducted along the equator between 145°E and 160°W during three cruises in November–December 1999, January 2001, and January–February 2002. Those cruises were covering the La Niña (1999, 2001) and the pre-El Niño (2002) periods. According to the sea surface temperature (SST) and nitrate concentrations in the surface water, three regions were distinguished spatially, viz., the warm-water region with >28 °C SST and nitrate depletion (<0.1 μmol kg⁻¹), the upwelling region with <28 °C SST and high nitrate (>4 μmol kg⁻¹) water, and the in-between frontal zone with low nitrate (0.1–4 μmol kg⁻¹). Picophytoplankton identified as the groups of Prochlorococcus, Synechococcus and picoeukaryotes showed a distinct spatial heterogeneity in abundance corresponding to the watermass distribution. Prochlorococcus was most abundant in the warm-water region, especially in the nitrate-depleted water with >150×10³ cells ml⁻¹, Synechococcus in the frontal zone with >15×10³ cells ml⁻¹, and picoeukaryotes in the upwelling region with >8×10³ cells ml⁻¹. The warm-water region extended eastward with eastward shift of the frontal zone and the upwelling region during the pre-El Niño period. On the contrary, these regions distributed westward during the La Niña period. These climatological fluctuations of the watermass significantly influenced the distribution of picophytoplankton populations. The most abundant area of Prochlorococcus and Synechococcus extended eastward and picoeukaryotes developed westward during the pre-El Niño period. The spatial heterogeneity of each picophytoplankton group is discussed here in association with spatial variations in nitrate supply, ambient ammonium concentration, and light field.  相似文献   

Recent Occurrences of Dinophysis fortii (Dinophyceae) in the Okkirai Bay, Sanriku, Northern Japan, and Related Environmental Factors     

Kazuhiko Koike  Hirotaka Otobe  Minoru Takagi  Tadahisa Yoshida  Takehiko Ogata  Takashi Ishimaru 《Journal of Oceanography》2001,57(2):165-175

Occurrence of Dinophysis fortii, a causative organism of diarrhetic shellfish poisoning, in the Okkirai Bay, Sanriku was surveyed in 1995, 1996, 1998 and 1999. In each year, its major occurrence was detected from the late May or early June and continued until the late June or early July. Seawater temperature, salinity and nutrients measurements suggested that inflows of offshore water into the bay played key role on the first major occurrence of D. fortii. With an analysis of continuous temperature data in the Otsuchi Bay which locates north of the Okkirai Bay, this influent was considered to be intermittent inflow of the offshore water by internal tidal waves which propagated from north to south. First occurrence peak of D. fortii was synchronous with phycobilin containing microalgae, synechococcoid cyanobacteria and cryptomonad, in all years. In vivo fluorescence measurement of D. fortii cells in 1995 and 96 showed that the cells in these microalgal-rich water contained more phycobilin pigment than those in the microalgal-poor water. The result may support a hypothesis that D. fortii acquires phycobilin by an uptake of these microalgae. After the first major occurrence in the bay, D. fortii sometimes occurred in rather inshore waters where showed elevated ammonium level possibly due to increased heterotrophic activity. Together with another finding that D. fortii is mixotrophic, it could be assumed that the environment being suited to heterotrophic nutrition also stimulates D. fortii growth in the bay.  相似文献   

基于ASTER VNIR-SWIR多光谱遥感数据识别与提取干旱地区岩性信息——以西南天山柯坪隆起东部为例     

时丕龙  付碧宏  二宫芳树 《地质科学》2010,45(1)

ASTER多光谱遥感数据目前可以用于岩石矿物资源信息的识别和提取。本研究尝试利用ASTER可见光近红外(VNIR)和短波红外(SWIR)的多光谱遥感数据提取干旱地区的岩石与矿物信息。基于新疆天山西南缘柯坪隆起东部不同地层单元岩石的化学组成和矿物成份以及VNIR-SWIR谱域光谱吸收特征的分析,我们采用相关吸收波段深度(RBD)和波段比值(BR)方法对研究区的多光谱遥感数据进行图像处理,有效区分和识别了白云岩、石灰岩、砂岩以及阿克苏群的蓝片岩—绿片岩和砂质片岩。白云岩的CO_3~(2-)吸收谱带中心波长位于2.32μm,与灰岩的CO_3~(2-)吸收谱带中心波长位置2.35μm相比,具有向短波长方向移动的特点,据此可以利用RBD7、RBD8分别有效的识别白云岩和灰岩;长英质岩石显示Al-OH和Fe~(3+)VNIR-SWIR吸收特征,而基性-超基性岩石显示Fe~(2+)和Fe、Mg-OH特征,利用不同的铁价态和次要矿物可以区分它们:ASTER band2/band1代表了含Fe~(3+)矿物分布信息、ASTER band5/band4代表了含Fe~(2+)矿物分布信息、RBD6可以估计Al-OH矿物的丰度;砂质/泥质片岩含较多的多硅白云母、绿泥石、黑硬绿泥石以及风化后表面覆盖的其它粘土矿物,在2.21μm(band6)存在有特征的吸收谱带,并且在1.65μm(band 4)具有较高的反射率,而蓝片/绿片岩在2.21μm(band 6)反射率较高,不具有明显特征吸收谱带,同时其在1.65μm(band 4)反射率较低,因此蓝片/绿片岩ASTER band4/band6比值低。应用ASTER band4/band6波段比值可以有效的区分开砂质/泥质片岩与蓝片岩/绿片岩。  相似文献   

Application of underwater optical data to estimation of primary productivity     

Makio C. Honda  Kosei Sasaoka  Hajime Kawakami  Kazuhiko Matsumoto  Shuichi Watanabe  Tommy Dickey 《Deep Sea Research Part I: Oceanographic Research Papers》2009,56(12):2281-2292

We conducted time-series observations of optical fields near the base of the euphotic zone (approximately 40 m) using moored automatic optical sensors at a time-series station in the Western Pacific Subarctic Gyre from March 2005 to July 2006 (with some gaps). We used the ratio of photosynthetically available radiation at the surface (surface PAR) to in situ quantum irradiance (in situ QI) at about 40 m as an index of opacity (surface PAR/in situ QI), which began to increase in the middle of April and peaked between the end of June and the middle of July 2005. This ratio then decreased toward winter. The ratio increased again beginning in January 2006, and large peaks were observed in June and July 2006. As an index of chlorophyll abundance we used the ratio of spectral irradiance at wavelengths of 555 and 443 nm (Ed₅₅₅/Ed₄₄₃) at about 40 m; seasonal variability of this ratio synchronized well with the attenuation coefficient “k” estimated with surface PAR, in situ QI, and BLOOMS depth. We estimated primary productivity (PP) using Ed₅₅₅/Ed₄₄₃ and an empirical equation based on a previous model but improved on the basis of shipboard observations. Estimated PP agreed well with observed PP. Seasonal variability of estimated PP was synchronized with that of organic carbon flux observed by sediment traps from approximately 150, 540, 1000, and 5000 m. This study demonstrates that time-series observations of in situ optical fields could contribute to the estimation of primary productivity and the study of the biological pump in the ocean.  相似文献   

Mapping hydrocarbon‐induced mineralogical alteration in the northern Tian Shan using ASTER multispectral data     

Bihong Fu  Guodong Zheng  Yoshiki Ninomiya  Chuanyuan Wang  Guoqiang Sun 《地学学报》2007,19(4):225-231

Seepage from hydrocarbon reservoirs can cause a number of chemical and/or mineralogical changes in overlying rocks and soils. These surface changes can be detected by remote sensing imaging systems. The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) is an advanced multispectral imaging system in the visible and near infrared (VNIR) to shortwave infrared (SWIR) region. Band ratios of ASTER VNIR and SWIR data to detect red bed bleaching and secondary carbonate formation induced by hydrocarbon seepage are proposed through analysis of the spectral properties of rock samples. Results show that ASTER band ratios of 2/1 and 4/8 can discriminate bleached red beds and secondary carbonate minerals due to hydrocarbon seepage in the northern Tian Shan. They are in good agreement with mineral identification using X‐ray diffraction. The ratio technique derived from ASTER data may provide a potential approach for hydrocarbon exploration in areas with sparse vegetation cover.  相似文献   

A new method for simulation of atmospheric effect on the emergent radiation over non-uniform terrain     

Tsutomu Takashima  Kazuhiko Masuda 《Earth, Moon, and Planets》1993,60(1):11-16

For a precise atmospheric correction over the non-uniform terrain in satellite imageries, a numerical method for evaluating the upwelling radiation at the top of the atmosphere bounded by the non-uniform surface is developed as an extended doubling-adding method. The present method enable us to treat quantitatively the case of hazy atmosphere and (or) large albedo of the surface.  相似文献   

Non-destructive elemental analysis of lunar meteorites using a negative muon beam     

I-Huan Chiu  Kentaro Terada  Takahito Osawa  Changkun Park  Soshi Takeshita  Yasuhiro Miyake  Kazuhiko Ninomiya 《Meteoritics & planetary science》2023,58(9):1333-1344

We report the result of a non-destructive elemental analysis of lunar meteorites using a negative muon beam at J-PARC. An experimental system of six Ge semiconductor detectors and a newly designed He analysis chamber (to enable quantitative analysis of Al) was used to provide a high signal-to-noise ratio for the detection of major elements from lunar rocks (Mg, Si, Fe, O, Ca, and Al). We performed a Monte Carlo simulation to determine the chemical compositions at two sides and the center of a sample (at depths of 0.33 and 0.96 mm below the sample surface, respectively) of the lunar meteorite DEW 12007. These results indicate that the three interior regions of DEW 12007 are likely to be 55.8:44.2, 51.4:48.6, and 54.4:45.6 wt% mixtures of anorthositic and basaltic clasts, respectively. This study is the first quantitative analysis of a heterogeneous meteorite interior using a negative muon beam. As elemental analysis using a muon beam is non-destructive and highly sensitive to light elements, including C, N, and O, the protocols established in this study are applicable to initial characterization of returned samples from the South Pole of the Moon.  相似文献   

Rainfall–runoff–inundation analysis of the 2010 Pakistan flood in the Kabul River basin     

Takahiro Sayama  Go Ozawa  Takahiro Kawakami  Seishi Nabesaka  Kazuhiko Fukami 《水文科学杂志》2013,58(2):298-312

Abstract

Pakistan has suffered a devastating flood disaster in 2010. In the Kabul River basin (92 605 km²), large-scale riverine and flash floods caused destructive damage with more than 1100 casualties. This study analysed rainfall–runoff and inundation in the Kabul River basin with a newly developed model that simulates the processes of rainfall–runoff and inundation simultaneously based on two-dimensional diffusion wave equations. The simulation results showed a good agreement with an inundation map produced based on MODIS for large-scale riverine flooding. In addition, the simulation identified flash flood-affected areas, which were confirmed to be severely damaged based on a housing damage distribution map. Since the model is designed to be used even immediately after a disaster, it can be a useful tool for analysing large-scale flooding and to provide supplemental information to agencies for relief operations.

Editor Z.W. Kundzewicz

Citation Sayama, T., Ozawa, G., Kawakami, T., Nabesaka, S. and Fukami, K., 2012. Rainfall–runoff–inundation analysis of the 2010 Pakistan flood in the Kabul River basin. Hydrological Sciences Journal, 57 (2), 298–312.  相似文献   

影响日本佐渡岛农民实施野生动物友好型耕作的因素探究(英文)     

中村慧  柘植隆宏  大久保悟  武内和彦  西川潮 《资源与生态学报(英文版)》2014,5(4):370-380

野生动物友好型耕作(Wildlife-friendly Farming,WFF)实践是一种维持农田生态恢复的良好方式。本研究的目的在于探讨影响日本佐渡岛农民实施WFF的因素和提出影响这种实践传播的政策。对佐渡岛上把大米销售给日本农业合作社(Japan Agricultural Cooperatives,JA)的5010个农户进行了问卷调查,总共收到2231农户反馈问卷(反馈率45%)。通过与未经认证农民的态度和属性对比,我们确定了影响农民实施WFF的关键因素。与未经认证的农民相比,已认证的农民:(1)对生物多样性和WFF的经济效益表现出更高的兴趣;(2)拥有更多的已认证农民朋友;(3)感受到了来自消费者的更多的压力和期望;(4)当实施WFF时,不受恶劣劳动力或农田条件的限制。为了在佐渡岛进一步宣传WFF,我们建议把WFF实践对稻田生物多样性的有效性信息应用到公共教育中,并在非认证农民和已认证农民之间、农民与消费者之间创建交流的机会。  相似文献